The Leahy Law and the Rule That US Weapons Not Go to Abusive Units

Patrick Leahy was a Vermont prosecutor before he was a senator, and he kept a prosecutor's habits. In the mid-1990s he was looking at American counternarcotics aid flowing to the security forces of Colombia, where the army and police were fighting guerrillas and drug traffickers and where human rights groups were documenting massacres, disappearances and collusion between some military units and right-wing paramilitaries. Leahy's question was narrow and practical: could the United States at least make sure it was not paying for the specific units doing the killing? In 1997 he attached a short provision to the annual foreign aid spending bill. It did not cut off any country. It did something more surgical, and in some ways more radical. It asked the government to look at each unit.

In short: The Leahy laws bar US security assistance to any unit of a foreign security force when there is credible information that the unit committed a gross violation of human rights, unless the foreign government is bringing those responsible to justice. The rule is simple, and vetting happens tens of thousands of times a year, but critics say it is enforced unevenly, especially for close allies.

Two laws with one name

There are really two Leahy laws, which is why people often speak of them in the plural.

The first covers assistance provided by the State Department under the Foreign Assistance Act and the Arms Export Control Act. It began as a provision in the foreign operations appropriations act, was broadened in the years after 1997 and is now permanent law. The second covers training, equipment and other assistance funded by the Defense Department. It began as a provision in the annual defense appropriations act and has since been placed in permanent law in Title 10 of the US Code.

The two versions are similar but not identical, and the differences matter to lawyers. The core is the same: no assistance to a unit of a foreign security force if the government has credible information that the unit committed a gross violation of human rights.

The words that do the work

Everything in the Leahy laws depends on a few phrases, so it is worth slowing down on them.

Gross violation of human rights. The State Department has generally treated this to include torture, extrajudicial killing, enforced disappearance and rape under color of law. These are the worst abuses, not every misconduct.

Credible information. The standard is deliberately lower than proof beyond reasonable doubt, or even a court finding. The government does not have to be certain. It has to have information that is believable enough to act on, from sources such as its own embassies, human rights groups, the press, UN reports and foreign governments.

Unit. The law looks at the specific unit that would receive the assistance and its chain of command, not the whole army. A battalion can be barred while the rest of a country's military keeps receiving aid.

Effective steps. The State Department version contains an exception: the bar can be lifted if the Secretary of State determines that the foreign government is taking effective steps to bring the responsible members of the unit to justice. This is called remediation. The defense version has a related exception and also allows a waiver in extraordinary circumstances.

Note what the law does not require. It does not require the United States to cut off a whole country. It does not require proof that American weapons were used in the abuse. And it does not depend on the President's judgment of foreign policy interests, except in the narrow ways the statute allows. Its default is a bar.

How vetting actually happens

Picture an American embassy that is about to bring a group of foreign police officers to a training course, or to deliver equipment to a particular brigade. Before that happens, the names of the individuals and the unit go into a vetting process.

Embassy staff check their own records and those of other US agencies. The request then goes to Washington, where the State Department's human rights bureau runs checks through a database and a team of analysts, consulting regional offices and intelligence holdings. If credible information of a gross violation turns up, the unit or individual is denied, and the decision is recorded.

This happens a very large number of times a year, across well over a hundred countries. Most requests are approved; a small share are denied or suspended. The process was built up over decades, and it has real teeth in many places. Units in countries from Latin America to Africa to South Asia have been cut off. In Colombia, where the law began, units were barred, and the pressure of the Leahy law is widely credited by human rights researchers and by some former officials with encouraging changes in how the military handled abuse cases, though the record there is also full of failures.

Where critics say it bends

The critique of the Leahy laws is not that they are unwise. It is that they are applied with different degrees of seriousness depending on who the recipient is.

One structural problem is how aid is delivered. Vetting works best when the United States knows exactly which unit will receive a training course or a piece of equipment. It is harder to apply to large transfers of weapons sold or financed for a whole military, where the specific end user is not identified in advance. Some of the largest aid programmes are built that way.

A second problem is the remediation exception. If a government says it is investigating, how long can the investigation run before the claim is not credible? Critics argue that in some cases the State Department has accepted assurances that were never followed by real accountability.

The sharpest criticism in recent years has concerned Israel, the largest recipient of US military aid. In 2024, former State Department officials and press reports described a separate, slower process for reviewing Israeli units, involving more senior officials and a higher bar before a finding could be made. That spring, the State Department said it had found five Israeli units responsible for gross violations of human rights in incidents before October 7, 2023, mostly in the West Bank, and that four had been remediated. The fifth, widely reported to be the Netzah Yehuda battalion, was later also judged remediated, and no Israeli unit was barred. Israeli officials said their military justice system investigates allegations and that the United States should not single out Israeli forces. Human rights groups said the outcome showed that no unit of a close ally would ever actually be cut off.

Supporters of the government's handling argued that Israel has an independent judiciary and a military justice system capable of punishing abuses, which is exactly what remediation is supposed to reward, and that vetting must take into account a partner's own accountability mechanisms.

The rule beside its cousins

The Leahy laws are not alone. Section 502B of the Foreign Assistance Act, from the 1970s, says that no security assistance may be provided to a government that engages in a consistent pattern of gross violations of internationally recognized human rights, unless extraordinary circumstances warrant it. It is broader than the Leahy laws, since it can apply to a whole government, but it has almost never been formally invoked. Section 620I of the same act bars security assistance to a country that restricts the transport or delivery of US humanitarian assistance.

In February 2024, the Biden administration issued a national security memorandum that required recipients of US weapons to give written assurances that they would use them in line with international humanitarian law and would not restrict US-supported humanitarian aid, and required reports to Congress. The resulting report in May 2024 said it was reasonable to assess that US-supplied weapons had been used in ways inconsistent with humanitarian law obligations in some instances, but said the government lacked complete information to reach conclusions about specific incidents, and it accepted Israel's assurances. In early 2025, the second Trump administration rescinded that memorandum. The Leahy laws, being statutes, stayed on the books.

What the law cannot see

Even a perfectly enforced Leahy law has blind spots, and honesty about them helps.

Vetting depends on information. In countries where journalists cannot work freely and human rights groups are harassed, abuses may never be documented well enough to count as credible information. The units most likely to commit atrocities in the darkest places are sometimes the least likely to be caught by a paper-based system.

Units also change. A battalion can be renamed, merged or split, and individuals can move from a barred unit to a clean one. Vetting individuals as well as units helps, but tracking them over years is hard.

Coverage is a further question. Whether and how vetting applies to weapons a foreign government buys with its own money, rather than through US grants or training, has been a subject of dispute, and some proposals in Congress have sought to make the coverage explicit. Equipment, once delivered, can also be moved from one unit to another. End-use monitoring exists, but it is thin compared with the volume of weapons sent abroad.

None of this means the law fails. It means it is a floor, not a ceiling, and that it works best alongside diplomatic pressure, public reporting and the work of investigators on the ground.

How Congress could make it stronger

Most of the improvements that experts and former officials have proposed are not dramatic, which is part of their appeal.

The first is staff and money. Vetting is done by a small office handling a very large caseload, and more analysts and better data systems would make reviews faster and more thorough. The second is transparency: annual public reporting of how many units were reviewed and denied, by country, with as much detail as security allows, would let Congress and the public see whether the rule is applied evenly. The third is clarity: writing into law exactly how vetting applies to different kinds of transfers, including large weapons packages for which the end-user unit is not specified in advance, would close the gaps that critics identify. A fourth would set time limits on remediation, so that an investigation that never concludes cannot keep a unit eligible indefinitely.

Each of these could pass with votes from both parties, and several have been proposed in some form before.

Why the rule is worth defending

Here is the argument for the Leahy laws, offered as this site's view.

The first reason is moral and very simple. The United States should not pay for torture or murder. Every taxpayer has a stake in that, whatever they think of a particular war.

The second is practical. Units that know they can be cut off have reasons to behave, and governments that want American training have reasons to punish the worst offenders. A unit-level rule creates incentives without cutting off whole alliances, which is why it has outlasted presidents of both parties and has drawn support from Republicans as well as Democrats in Congress.

The third is about the rule of law at home. A statute that is applied rigorously to small countries and loosely to big allies teaches every government that American law is a matter of relationships. That corrodes the credibility of every human rights argument the United States makes. Applying the same standard to friends is harder, and it is the point.

There is an honest self-criticism for progressives too. Leahy vetting is mostly invisible, technical work done by mid-level civil servants, and the left has often focused on dramatic demands, such as cutting off all aid to a country, instead of defending and funding the unglamorous machinery that already exists in law. A bigger, better-staffed vetting office and public reporting on denials would do more good than many slogans.

The prosecutor's question

Leahy retired from the Senate in January 2023, after nearly half a century. The rule named for him outlived his career, and the question he asked in the 1990s is still the right one: not "is this country our friend?" but "did this unit do this, and is anyone being held to account?" It is a narrower question than most foreign policy debates, and it has the virtue of being answerable.

You can follow arms transfers, aid debates and the use of American weapons abroad on our Pentagon and militarism topic page and on the human rights and foreign aid page.

What you can do

• Ask your senators one precise question. Senators vote on arms sales and approve the budget for vetting. The representatives page gives you their phone numbers and contact forms from your address and shows their latest votes. Ask: will you support public reporting on how many units are denied under the Leahy laws, country by country?
• Look for bills that touch arms transfers. Our Congress votes and bills tracker lists recent recorded votes, including resolutions on arms sales, so you can see where your members stood.
• Look for agreement across the aisle. The Leahy laws have had bipartisan backing. The common ground page lists bills both parties passed together, a useful reminder that human rights conditions do not have to be a partisan fight.
• Support the people documenting abuses. Vetting depends on credible information, and much of it comes from human rights researchers and journalists. Find civil rights and legal aid groups in your state through the organizations directory.