Shortly after Israel killed seven World Central Kitchen workers in a marked aid convoy in Gaza, US National Security Council spokesman John Kirby said the State Department “has not found any incidents that the Israelis have violated international humanitarian law”.
The assertion is crucial for the US, as under its own rules, most notably the Leahy Law, it cannot supply arms to foreign military units that are breaking humanitarian law.
The US has long stated that its support of Israel is “ironclad” and refused to put any conditions on how American bombs are used in Gaza.
Local health authorities say more than 34,600 people have been killed there since the October 7 Hamas attacks on Israel, in which 1,200 people died.
But that position may now be changing. Axios reported at the weekend that Washington has stopped a planned ammunition shipment to its ally.
The White House and State Department declined to comment on the report.
The Leahy Law, or Leahy Amendments, prohibit US assistance to foreign security forces when there is credible information that a unit has committed a “gross violation of human rights”.
One statute is applicable to the State Department and another to the Department of Defence.
That emphasis on units is distinct, “because it does not require a decision to cut off aid to an entire country – which the US government is often reluctant to do", Amnesty International said.
"Rather, it tackles the challenge by prohibiting aid solely from the offending units."
President Joe Biden's Democratic Party has repeatedly expressed concern that Israel is breaking international law in Gaza.
The State Department Leahy Law also includes an exception allowing assistance to a unit to resume if the Secretary of State determines and reports to Congress that the government of the country is taking effective steps to bring those responsible to justice.
The law is named after former Democratic senator Patrick Leahy, who was its chief sponsor.
The amendments that became the Leahy Law date back to appropriations provisions he led in the 1990s during efforts to control US military aid to Colombia.
Washington at the time was assisting with anti-drug trafficking work and crackdowns on leftist insurgents there.
The law was used during former president Barack Obama's administration to cut military aid to Pakistani units as punishment for human rights abuses, including torture and extrajudicial executions.
Now retired, Mr Leahy has voiced concerns that US support for Israel's war in Gaza has breached his namesake policy.
“On this one, I think that there are violations of the Leahy Law,” he recently told Vermont local media.
In implementing the Leahy Law, US government considers torture, extrajudicial killing, forced disappearance and rape under colour of law to be gross violations of human rights.
Incidents are examined on a fact-specific basis, according to the State Department.
“I’m not in the Senate. I can’t fight about it … I’m not the chair of the committee," Mr Leahy said.
"But everybody who’s asked me in the international press, the national press, I’ve said to them: I think there are violations of the Leahy Law."
Last week, Washington accused five Israeli military units of committing “gross violations of human rights” in the occupied West Bank before October 7, although it has avoided addressing those concerns about conduct in Gaza.
Washington gives Israel about $3.3 billion of foreign military financing every year, which is subject to the Leahy Law.
Arms sales are not subject to the Leahy Law because they are considered to be commercial transactions, not assistance.
The State Department in 2020 set up a special forum for Israel to try to identify units that have committed gross violations of human rights. To date, there have been no such findings.
The Leahy Law's existence has been used to check some progressive Democratic pushes against strengthening oversight on potential Israeli human rights abuses since the war in Gaza began.
Earlier on in the war, those efforts materialised into the Van Hollen amendment, which would require “weapons received by any country under the proposed national security supplemental [be] used in accordance with US law, international humanitarian law and the law of armed conflict”.
But Senate foreign relations committee chairman Ben Cardin cast doubt on the effort.
Mr Cardin told The National in December that he “does not believe it's necessary to condition aid further than was already conditioned, as far as US military assistance is concerned”.
“I certainly support the Leahy principles," he said. "We'd be very interested in having a further review on [their application]."
After the deaths of the World Central Kitchen aid workers, one of whom was a dual US-Canadian citizen, new questions were asked about Israel's compliance with international law.
Democratic Senator Chris Coons, an ally of Mr Biden, endorsed Washington placing conditions on aid to Israel “if they continue with large-scale military operations in Rafah without making any provisions for civilians”.
“I've never said that before; I've never been here before,” Mr Coons said.
“The tactics by which the current Prime Minister [Benjamin Netanyahu] is making these decisions don't reflect the best values of Israel or the United States.”
In a letter to Mr Biden, senior Democratic members of Congress “strongly urged” that he reconsider his recent decision to authorise a new arms package to Israel and to “withhold this and any future offensive arms transfers until a full investigation into the air strike is completed”.
Signatories included establishment Democrat and former House speaker Nancy Pelosi, who had previously accused pro-ceasefire demonstrators of being loyal to China and Russia.
“If this strike is found to have violated US or international law, we urge you to continue withholding these transfers until those responsible are held accountable,” the letter continued.
“We also urge you to withhold these transfers if Israel fails to sufficiently mitigate harm to innocent civilians in Gaza.”
