The Treaty Clause of Article II is one of the highest bars in American law. It was designed by the framers to force broad consensus on the nation's international commitments. In practice, in a polarized Senate, it means that a determined minority of 34 senators can block any treaty, regardless of its merits or the president's support. This is the reason several major, carefully negotiated treaties never entered into force for the United States, not a hypothetical constraint.

In a polarized Senate, that threshold is where ambitious treaties go to die. Any serious plan for an AI agreement has to reckon with it from the start.

A history of treaties killed at home

  • The Comprehensive Nuclear-Test-Ban Treaty (1999). Signed by the US and central to non-proliferation, it was rejected by the Senate 48-51, far short of 67. The US has still never ratified it.
  • The UN Convention on the Law of the Sea. Supported by the military, industry, and successive presidents of both parties, it has sat unratified for decades because it cannot reach 67 votes.
  • The Kyoto Protocol. The Senate pre-emptively voted 95-0 for a resolution opposing it, and it was never even submitted for ratification.
  • The Convention on the Rights of Persons with Disabilities (2012). Rejected despite bipartisan backing and modeled on existing US law, falling five votes short.

The pattern is clear: even treaties with broad expert support, presidential backing, and allied pressure routinely fail to clear the Senate. An AI treaty (likely to be attacked as a surrender of sovereignty, a constraint on a strategic industry, and a concession to China) would face at least as steep a climb.

Why an AI treaty is especially vulnerable

The specific objections write themselves. Opponents will argue that binding limits hand an advantage to adversaries who will cheat; that verification amounts to letting foreigners inspect American labs; that the treaty smothers a critical industry; and that it cedes decisions about national security to an international body. Each of these arguments has sunk treaties before, and each maps directly onto the AI debate. A treaty that requires 67 votes in this environment is, on its face, a daunting proposition.

The paths around the two-thirds bar

1

Congressional-executive agreements

Not every binding international commitment is an Article II treaty. Many (including most US trade agreements) are approved by a simple majority of both houses as congressional-executive agreements. Courts have treated these as constitutionally interchangeable with treaties for most purposes. This route needs 51 Senate votes plus the House, not 67.

2

Sole executive agreements

The president can make certain binding commitments without Congress at all, within the scope of executive power. These are legally limited and can be undone by a successor, but they can carry initial commitments while broader ratification is pursued, the mechanism behind US adherence to the Paris Agreement.

3

Domestic legislation mirroring the treaty

Congress can enact the substance of an international standard as ordinary law by simple majority, binding US actors to the same obligations without formal ratification of the treaty itself. Compute and export controls already show this route in action.

4

Build durable bipartisan salience

The only path to actual ratification is making AI risk a genuinely cross-partisan concern, so that 67 votes becomes conceivable. That is a political project (the work of shifting the issue from partisan to consensus) that has to begin years before any treaty reaches the floor.

A treaty that cannot pass the Senate is a press release. Serious AI diplomacy has to be designed backward from 67 votes, or designed to use the binding instruments that do not need them.

Designing for the domestic constraint

The lesson is not despair but design. The two-thirds bar is real, but it is not the only door. A well-constructed ASI governance strategy would combine instruments: domestic legislation and executive action to establish immediate commitments, congressional-executive agreements where a simple majority is achievable, and a long-term political effort to build the bipartisan consensus that formal ratification would require. It would also shape the treaty's content to blunt the predictable objections, reciprocal verification rather than one-way inspection, protections for legitimate industry, and safeguards for national security. The mistake is to negotiate a treaty abroad while ignoring the arithmetic at home. In the American system, the hardest negotiation is often the one in the Senate, and it has to be planned for from the first day.