Transferring weapons and weapon parts to Israel has become an increasingly controversial topic in the US and has often led to public negativity and scrutiny. Criticism and public calls for suspensions of such transfers have become more frequent during the current war in the Middle East.  

Hamas’ murderous attack against Israel of 7 October set forth a chain reaction of events in the region: the full-scale land invasion of Gaza where combat and intelligence-driven Counter–Insurgency (COIN) operations continue; the full spectrum war in Lebanon against Hezbollah since October 2024; the disruption of vital shipping in the Red Sea through Houthi forces, and the subsequent US/UK led international maritime force response; the ongoing military conflict with Iran, which saw the targeting of Iranian and its affiliates’ so-called High Value Targets; two Iranian aerial attacks on Israel, and subsequent Israeli retaliation highlight the volatility of today’s conflict. 

Sustaining combat readiness and military capabilities is a top priority for Israel and while Israel is the world’s ninth largest weapon producer it is also heavily dependent on foreign weapons imports. According to the Stockholm International Peace Research Institute (SIPRI), Israel received 69 percent of its weapons imports from the US between 2019 and 2023. Before this background, it is important to look into the law governing the provisions of US military aid to Israel and the question of when such support becomes illegal under US and, potentially, international law. 

The transfer of arms is internationally regulated under the Arms Trade Treaty (ATT) of 2013, which “regulates international transfers of conventional arms, ammunition, and parts and components,” and forbids such transfers “when there is a defined level of risk that war crimes or serious violations of international human rights law will be committed.” 111 states to date have signed and ratified this humanitarian safeguard of arms transfers. The US, after having been fundamental under the Obama administration in negotiating the ATT, signed it in 2013. In 2019, not having ratified the treaty, the US withdrew its signature under then President Donald Trump. 

In absence of the ATT, limitations for the US regarding arms transfers arise under both international and domestic law: the U.S. Conventional Arms Transfer Policy (CAT), updated in 2023 by the Biden administration, limits and even prohibits US arms transfers where there is the danger that those weapons can be used by a recipient in violation of International Humanitarian Law (IHL) as well as Human Rights Law.   

CAT is the US domestic response to the (universal) state duty to respect and ensure respect for IHL in all circumstances including such arms transfers under Article 1, common to the  1949 Geneva Conventions, and Article 1 of Additional Protocol to the Geneva Conventions. According to the International Committee of the Red Cross (ICRC), this duty obliges all states including the US  to “refrain from transferring weapons where there is a clear risk that this would contribute to IHL violations, and they must do everything reasonably in their power and take positive steps to ensure respect for IHL by parties to armed conflict.” The US CAT aims to ensure compliance with this duty to comply with IHL and extends it to Human Rights compliance as well when it comes to arms transfers. 

In addition to arms transfers, the rendering of financial assistance to foreign security units is restricted under the provisions of the so-called Leahy Law, two statutory provisions which apply to the Department of State (DoS) (section 620M of the Foreign Assistance Act of 1961, 22 U.S.C. 2378d. ) and the Department of Defense (DoD) (Section 362 of Title 10 of the U.S. Code). Credible information that the unit which is to benefit from DoD or DoS funding is implicated in the commission of gross violations of human rights (such as extrajudicial killings, forced disappearance, torture etc) makes such assistance illegal under US law. Rendering of assistance to the Israeli military deployed in the occupied/disputed territories of the West Bank raises such Leahy Law legality questions. US Secretary of State Antony Blinken “determined that four Israeli units had committed gross violations of human rights but that Israel had taken corrective action sufficient to remediate the violations, rendering those units eligible for assistance.” This decision was, unsurprisingly, met with criticism. 

Returning to the original issue of the legality of US arms transfers to Israel, the pertinent question is whether there is the danger that Israel would be using these arms in violation of IHL and Human Rights Law. The wars in both Gaza and Lebanon have seen widespread international criticism of Israel’s execution of the war by the UN and NGOs, public protests globally (including the rise of widespread antisemitism), and an ongoing investigation by the International Criminal Court into potential war crimes, including an application for arrest warrants by its Chief Prosecutor.  

To date, the US has only slowed down but never suspended arms transfers to Israel. The DoS assessed the conduct of Israel’s military in Gaza and found in a report of May 2024, the National Security Memorandum 20 (NSM-20), that “weapons might have been used in violation of humanitarian law (in individual instances) and that Israel (might have) acted in ways that have blocked U.S. humanitarian assistance.” The report stopped short of making any recommendations of suspending arms transfers under CAT as, overall, Israel was not non-compliant with its IHL obligations. It was important for the authors of the report to point out that the NSM-20 was an incentive for Israel to work towards compliance with its international obligations.

In regards to the issue of humanitarian assistance, in October the US threatened that it would withhold military aid to Israel if humanitarian aid to Gaza would not improve. One month later, the Biden administration announced that it would not limit arms transfers to Israel any longer as there had been sufficient improvements regarding the delivery of humanitarian aid to Gaza. This latest announcement also stressed that the administration did not make an overall “assessment that the Israelis are in violation of US law or not” and continued to monitor the situation. 

The complexity of the battlefield, its main actors, the difficulty in verifying claims of IHL violations as well as casualty figures or the impact Hamas and its affiliates have on the delivery of humanitarian aid makes it hard to make conclusive findings in regards to IHL and US law compliance or non-compliance. Before this backdrop, it is hard to argue that the Biden administration did not fulfill its international and US legal obligations in terms of conducting a valid pre-transfer assessment of the risk that the delivery of weapons to Israel could be used to violate IHL or human rights.  

This overall finding is important in the context of the fact that the incoming administration of Donald Trump will be even more supportive of Israel and be less inclined to request more safeguards of IHL compliance from Israel. Given the current safeguards under CAT and the incentive of the NSM-20 IHL compliance assurance requirement, US military support to Israel could continue even without the next administration being tempted to violate its legal obligations. As long as the US continues to monitor and assess IHL compliance there is little risk of the US violating international IHL and domestic arms transfer legal safeguards.   

Sascha-Dominik (Dov) Bachmann is Professor in Law and Co-Convener National Security Hub (University of Canberra), University of Canberra, and a Research Fellow with the Security Institute for Governance and Leadership in Africa, Faculty of Military Science, Stellenbosch University. Sascha is a Fellow with NATO SHAPE ATO (Hybrid War and Lawfare Pacific) and an affiliated Researcher at the Risk and Crisis Centre, Mid Sweden University.

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