Can Sanders' Billionaire Tax Survive Constitutional Review?

Bernie Sanders’s February 2026 Los Angeles remarks made the billionaire tax sound like a democratic-accountability fight: he said the billionaire class believed it had “the divine right to rule” and was “no longer subject to democratic governance.” That language matters politically, because it turns tax design into a claim about who governs. The litigation question is narrower and less forgiving: what kind of tax is this, and which government has the constitutional power to impose it? After Moore v. United States, neither side can honestly say the answer is settled.[1][2][3]

Publication category: Regulation & Ethics. Last verified: August 3, 2026, 00:00 UTC. Reviewed for legal background by Mara V. Chen, J.D. This article is legal-risk analysis for general information only, not legal or tax advice. Source note: the analysis relies on the federal bill materials, the California initiative text, Moore v. United States, and attributed legal analyses from tax-policy and law-firm sources.

The chronology is short but useful. The California 2026 Billionaire Tax Act was filed with the California attorney general on October 22, 2025, and amended on November 26, 2025.[4] Sanders spoke at the Wiltern Theater in Los Angeles on February 18, 2026, before a reported crowd of about 2,000 people.[1][2] On March 2, 2026, Sanders and Rep. Ro Khanna introduced the federal Make Billionaires Pay Their Fair Share Act, described as a 5% annual tax on billionaire wealth.[5][6] Ballot qualification for the California measure was reported in June 2026, with the election scheduled for November 3, 2026; the certification details and any proposition-number designation should still be checked against official California election records before relying on them in a filing or client memorandum.[7][8]

The same slogan is traveling through two constitutional systems

The federal and California proposals are easy to collapse into one political story. They should not be collapsed legally. The federal bill runs straight into the Constitution’s direct-tax architecture: Article I’s apportionment rule and the 16th Amendment’s exception for taxes on incomes. California does not face that federal apportionment command. Its problem is different: a one-time, retroactive taxpayer snapshot, with resident status fixed at one date and wealth valued at another.

That distinction is where most public commentary goes wrong. Moore did not kill wealth taxes. It also did not bless them. It upheld a specific federal tax on shareholders of a controlled foreign corporation by treating the tax as an attribution of realized corporate income to shareholders. The Court then deliberately refused to decide whether realization is constitutionally required for income taxation.[3]

What Moore actually decided

Moore concerned the mandatory repatriation tax, not a general wealth tax. Charles and Kathleen Moore had invested in KisanKraft, an Indian company. The tax at issue reached their share of the company’s accumulated income, and the Moores paid $14,729 in tax on roughly $508,000 of KisanKraft income that had not been distributed to them.[3]

Justice Kavanaugh’s majority opinion, in a 7-2 judgment, upheld the tax on a relatively narrow rationale: Congress may attribute realized income of an entity to its shareholders or partners and tax those shareholders or partners on that attributed income. The opinion described attribution as a legislative choice with deep roots in partnership, S corporation, and controlled-foreign-corporation regimes.[3]

The sentence that matters for the 2026 billionaire-tax debate is the Court’s reservation: “we do not decide that question today” on realization. That is not a throwaway line. It is the doctrinal space in which both the federal wealth-tax challenge and the defense of income-style alternatives now sit.[3]

The separate opinions make the uncertainty harder to smooth over. Justice Barrett, joined by Justice Alito, concurred in the judgment but took a stricter view of realization than the majority. Justice Jackson concurred separately and was more open to Congress taxing unrealized gains as income or as non-direct taxes. Justice Thomas, joined by Justice Gorsuch, dissented and treated realization as constitutionally necessary for income under the 16th Amendment.[3]

That configuration does not yield a clean post-Moore rule for a tax on annual net worth. A government defending a tax that reaches unrealized appreciation would have language to quote. A challenger would have language to quote. Neither would have a holding squarely on point.

The federal 5% tax faces the direct-tax problem first

The federal proposal is described by its sponsors as a 5% annual tax on the wealth of the country’s billionaires. Sanders’s release identified 938 U.S. billionaires with about $8.2 trillion in wealth and cited a Saez-Zucman estimate that the tax would raise $4.4 trillion over ten years, assuming 10% evasion.[5] Forbes reported the same 5% annual design and also noted competing revenue estimates, including a lower figure associated with Kyle Pomerleau.[6]

Those revenue numbers explain why the proposal has political force. They do not answer the constitutional question. If a federal 5% annual levy is treated as a tax on net worth itself, the central objection is direct: a federal direct tax must be apportioned among the states by population unless the 16th Amendment removes that requirement. The 16th Amendment removes apportionment only for taxes “on incomes,” and an annual tax on balance-sheet wealth is not obviously a tax on income.[3]

The strongest defense does not pretend that the bill is ordinary income taxation. Ari Glogower, David Gamage, and Darien Shanske Richards have argued that an unapportioned federal wealth tax can be constitutional under a more flexible reading that distinguishes a tax measured by wealth from the narrow class of direct taxes that must be apportioned.[9] That argument matters because constitutional tax categories have not always tracked economic labels with perfect neatness.

But the defense has to carry a heavy burden after Moore precisely because Moore avoided deciding the harder question. The Tax Foundation has treated the Sanders bill as constitutionally vulnerable, arguing that a wealth tax is a direct tax and that apportionment would make it unworkable.[10] City Journal likewise characterizes the proposal as unconstitutional and emphasizes the burden of a 5% annual rate, including the point that a 5% wealth tax can function like a 100% tax on a 5% annual return.[11] That equivalence is economic shorthand, not a constitutional test, but it captures why valuation and liquidity would become litigation facts rather than campaign abstractions.

Post-Moore commentary is also more cautious than many political summaries. A Syracuse Law Review comment reads Moore’s narrow holding as not necessarily making a wealth tax a stronger possibility.[12] That is the more defensible reading. Moore preserved existing pass-through and anti-deferral regimes; it did not decide whether Congress may impose an unapportioned annual levy on net worth.

The revenue estimates should stay in that lane. Saez and Zucman’s $4.4 trillion estimate assumes 10% evasion.[5] The Tax Foundation’s lower estimate of about $3.3 trillion assumes roughly 33% evasion using an elasticity of -8.[10] Pomerleau’s still lower estimate, reported at about $2.3 trillion, reflects a different modeling approach.[6] These are model outputs, not money in the Treasury and not evidence that the tax is or is not constitutional.

California moves the fight away from apportionment and toward the snapshot

The California measure is legally more interesting because the federal apportionment objection does not simply transplant into state court. States have broader authority to tax their residents, including resident wealth connected to worldwide assets. That does not make the California 2026 Billionaire Tax Act safe. It means the challenge migrates: retroactivity, apportionment under dormant Commerce Clause doctrine, mobility, valuation, and the measure’s self-description as a one-time excise become the exposed parts.

The initiative text imposes a one-time 5% tax on net worth above $1 billion for covered residents and part-year residents, using January 1, 2026, for taxpayer status and December 31, 2026, for valuation.[8] That drafting choice is not incidental. It attempts to prevent avoidance by people who would move after the campaign became visible, but it also creates the constitutional friction: the measure asks voters in November 2026 to approve a tax tied partly to a status date at the beginning of that same year.

The fiscal claims are again estimates. The ITEP-published expert report describes 213 California billionaires with $2.182 trillion in wealth, or 26.6% of U.S. billionaire wealth, and projects about $100 billion in revenue from 2027 through 2031.[14] The initiative text allocates 90% of proceeds to health and 10% to education and food assistance.[8] Those allocations may matter politically and for state-law analysis, but earmarking does not cure a federal constitutional defect if one exists.

Retroactivity is the most obvious target

Tax Foundation’s California analysis puts the retroactivity issue at the center, contrasting older Supreme Court cases such as Blodgett v. Holden and Untermyer v. Anderson with the more forgiving modern framework of United States v. Carlton.[13] The older cases struck down certain retroactive gift-tax applications as arbitrary and harsh. Carlton upheld a retroactive tax amendment where Congress acted promptly and rationally to correct an unintended revenue loss.

The California measure is not a simple Carlton-style correction of a drafting error. It is a voter-enacted tax designed from the start to reach a prior status date. That does not automatically make it unconstitutional. It does make the justification do real work. The drafters will say the retroactive snapshot is necessary to prevent billionaires from defeating the tax by moving after the measure becomes politically salient. Challengers will say that the state cannot impose a new one-time tax on people by looking backward to a date before enactment and then valuing assets at year-end.

The ITEP-published expert report defends the design as a one-time excise and points to California precedent, including the 2012 Proposition 30 income-tax increase, as support for retroactive tax changes under state law.[14] That defense is serious, but it has to bridge an important difference: an income-tax rate increase for a tax year already underway is not identical to a new one-time wealth levy keyed to a billionaire-status snapshot.

Departing taxpayers create the apportionment and travel arguments

The next vulnerability is the treatment of people who were California residents on January 1 but later leave. Tax Foundation frames this as a fair-apportionment problem under Complete Auto Transit v. Brady, especially if the measure taxes a former resident’s full worldwide wealth without sufficiently accounting for the person’s changed connection to California.[13] The argument is not the federal direct-tax apportionment argument. It is the dormant Commerce Clause version: whether the state tax is fairly apportioned to the taxpayer’s in-state connection.

The right-to-travel theory is adjacent but distinct. Tax Foundation flags Shapiro v. Thompson as part of the challenge map, arguing that a tax design penalizing interstate movement could trigger constitutional scrutiny.[13] That theory will turn on how courts characterize the burden. A tax that merely prevents avoidance may be seen differently from a tax that punishes leaving California.

Baker Botts catalogues a broader set of federal and state challenge theories, including due process, Commerce Clause, equal-protection, and California-law objections.[4] AEI’s criticism adds another strand: if the measure is labeled an excise to avoid some objections, courts may still ask what the tax actually reaches in operation.[15] That is the recurring problem with wealth-tax drafting. Labels help; base design decides much of the fight.

Two verification points should not be cleaned up too quickly

First, the treatment of intangible property needs a final text check. The ITEP expert report and Baker Botts discussion appear to report different figures for an intangible-property tax cap, with ITEP using 0.4% and Baker Botts using 0.04%.[14][4] Before anyone treats that as a settled drafting feature, it should be verified against the California DOJ initiative text and any later official ballot version.

Second, reported ballot qualification in June 2026 is a litigation-risk trigger, not a substitute for the official record. CalMatters reported qualification, but ballot certification details and any proposition number should be confirmed through California election materials before publication of a formal legal opinion.[7]

Why international examples and “fair share” rhetoric do less legal work than they seem to

International wealth taxes can help explain behavior and avoidance concerns. They do not answer the U.S. constitutional question. Tax Foundation and City Journal both emphasize that a 5% annual wealth tax would be unusually high by OECD standards and point to taxpayer mobility concerns, including reports about wealthy residents leaving Norway after wealth-tax increases.[10][11] Those examples may influence policy judgment, revenue modeling, and legislative drafting. They are not authority on Article I, the 16th Amendment, due process, or the dormant Commerce Clause.

The same is true of billionaire net-worth rankings. They make the democratic-accountability argument vivid. They may help explain why campaigners describe concentrated wealth as a governance problem. They do not decide whether Congress has taxed income or wealth, whether California has imposed a permissible one-time excise, or whether a retroactive snapshot is rational and fairly apportioned.

Design alternatives reveal the constitutional pressure point

The existence of alternative billionaire-tax designs is legally revealing. Mark-to-market systems, Wyden-style billionaire minimum income taxes, Biden-style billionaire minimum income tax proposals, exit taxes, and renunciation rules are attempts to tax income, deemed realization, or departure events rather than impose a pure annual tax on net worth.[16]

Those alternatives are not automatically constitutional either. They raise their own valuation, liquidity, realization, and administrability questions. But they show why the federal Sanders-Khanna design is the harder federal path: when the base is annual wealth itself, the government has less room to shelter behind the 16th Amendment’s income-tax language.

That leaves the 2026 map genuinely open. The federal bill faces the more formidable constitutional obstacle because an unapportioned annual net-worth tax has to get past the direct-tax problem that Moore did not resolve. California’s measure is more likely to generate the practical litigation fight this year because it is on the ballot track, but its vulnerability sits elsewhere: the retroactive taxpayer snapshot, the treatment of departing residents, and the effort to characterize a wealth-based levy as a one-time excise.

References

1. Bernie Sanders rails against billionaire greed amid California tax battle, The Guardian, February 19, 2026.
2. Sanders billionaire tax rally, CalMatters, February 2026.
3. Moore v. United States, Supreme Court of the United States, June 20, 2024.
4. California 2026 Billionaire Tax Act, Baker Botts, December 2025.
5. NEWS: Sanders and Khanna Introduce Legislation to Tax Billionaire Wealth and Invest in Working Families, Office of Senator Bernie Sanders, March 2, 2026.
6. Sanders And Khanna Push National 5% Annual Billionaire Wealth Tax, Forbes, March 3, 2026.
7. California unions billionaire tax ballot, CalMatters, June 2026.
8. California 2026 Billionaire Tax initiative text, California Department of Justice.
9. The Constitutionality of a Federal Wealth Tax, Indiana University Maurer School of Law Faculty Publications.
10. Bernie Sanders Wealth Tax on Billionaires, Tax Foundation.
11. Bernie Sanders and Ro Khanna’s Billionaires Wealth Tax, City Journal.
12. Narrow Holding in Moore v. United States Does Not Undermine Traditional Tax Principles, Syracuse Law Review.
13. California Billionaire Wealth Tax: Legal Challenges, Tax Foundation.
14. Expert Report on the California 2026 Billionaire Tax: Revenue, Economic, and Constitutional Analysis, Institute on Taxation and Economic Policy.
15. When Is a Tax Not a Tax?, American Enterprise Institute.
16. Everything You Need to Know About Billionaire Tax Proposals, Institute on Taxation and Economic Policy.