[Read the Complementarity Legal Opinion here]
On 11 June 2026, Lawyers for Palestinian Human Rights (LPHR), published a 142-page independent technical legal opinion by international law experts at Doughty Street Chambers, Megan Hirst and Nikila Kaushik1, that crucially assesses the application of complementarity to the International Criminal Court (ICC) Prosecutor’s investigation of the Palestine Situation.
The legal opinion is thorough, clarifying and vital. It finds that considerable gaps in Israel’s legal framework, and material omissions in the operation of Israel’s military justice system, will seem to prevent in the Netanyahu and Gallant cases, and in many other potential ICC cases, an effective complementarity challenge. This conclusion is critical for prospects of attaining holistic accountability at the ICC for systematic violence and persecutory policies in Palestine since 2014.
LPHR confidentially submitted the authoritative independent legal opinion to the ICC’s Office of the Prosecutor (OTP) last month. Its fundamentally important findings should embolden the OTP to take forward further cases for prosecution before the ICC in the Palestine Situation.
What is “complementarity” and why does it matter?
The principle of complementarity establishes that the ICC only operates as a court of last resort. This means that a matter will only be admissible before the ICC where it is not subject to domestic criminal investigation or prosecution. Applying the principle of complementarity to a specific case can result in preventing allegations of international crimes from being prosecuted at the ICC.
Complementarity is therefore a necessary obstacle to overcome if legal accountability for those most responsible for atrocity crimes, and justice for an enormous number of Palestinian victims and survivors, is to be ultimately achieved at the ICC.
If the OTP assesses that there is sufficient evidence that complementarity might be successfully invoked by a State with jurisdiction, or a particular suspect, it may decide not to bring the case for prosecution before the ICC. Complementarity can therefore be a legitimate basis for the OTP to decline to progress a case to prosecution despite otherwise assessing that there are reasonable grounds to believe that a particular suspect has committed a crime within the ICC’s jurisdiction.
Alternatively, where the OPT has assessed that a case is fully admissible for prosecution, a State with jurisdiction or a particular suspect may bring a complementarity challenge to be determined by the ICC before trial. A successful complementarity challenge would immediately end the case. It seems certain that the State of Israel, or a particular suspect, would attempt to bring a complementarity challenge at the relevant time in a case brought against an Israeli national before the ICC.
Background to the complementarity legal opinion and its key findings
LPHR assessed that it is vital to provide thorough legal clarity on the application of complementarity to the Palestine Situation. Two specialist international criminal law practitioners – Megan Hirst and Nikila Kaushik of Doughty Street Chambers – were instructed by LPHR to prepare a comprehensive legal opinion that may be authoritatively relied upon by decision-makers and lawyers. The work was undertaken on the basis that full payment be made irrespective of its legal conclusions.
Their 142-page legal opinion was finalised last month. Sections on Israeli law were reviewed by a lawyer qualified in Israel to confirm accuracy. The legal opinion forensically focuses on the substance of Israel’s legal framework for prosecuting international crimes and the operation of its military justice system. Its analysis includes examination of three major Gaza-specific case studies:
the seven-week hostilities between Israel and Palestinian armed groups in Gaza in 2014;
Israel’s use of force during large-scale protests in Gaza in 2018-19; and
the intensification of hostilities in Gaza in 2023-25 (the UN Independent International Commission of Inquiry finding that Israel’s conduct constitutes the crime of genocide).
LPHR encourages wide readership of this exemplary legal opinion in full and its opening Executive Summary. We nonetheless conclude this statement with excerpts that illuminate its key findings:
“Our review of the ICC’s practice to date underscores the fundamental importance of the first step in a complementarity analysis: activity. Although analysis and commentary often focus on the “unwillingness” (and/or “inability”) component of complementarity, our conclusions are shaped by the fact that the bulk of the ICC’s complementarity decisions to date have been determined on the basis that the activity requirement was not met, without proceeding to the second part of the test.” (Para. 7, Executive Summary)
“For those who seek to argue that an ICC case is admissible, the activity requirement is the strongest weapon. The concept has been interpreted expansively, including to encompass some factors which might at first glance appear to suggest unwillingness or inability. And whether consciously or not, ICC judges appear to be more open to concluding that institutions have simply not acted, rather than to finding that judicial actors lacked independence or impartiality.” (Para. 8, Executive Summary)
“Moreover, in the Israeli legal system, there are compelling reasons why a finding of inactivity appears likely, if not inevitable, in respect of the publicly known cases currently before the ICC, as well as other possible ICC cases.” (Para. 9, Executive Summary)
“As a question of domestic law, it may simply be impossible for relevant proceedings to be brought in Israel, with the result that they do not occur (that is, inactivity). This is because Israeli law does not contain domestic offences which address the conduct covered by many international crimes. Israeli law prohibits genocide and contains a small number of military offences comparable to some war crimes. However, many war crimes and crimes against humanity concern conduct which is simply not criminalised in Israel. Israeli law also does not contain forms of liability mirroring those often used by the ICC to charge commanders and military superiors. These legal lacunae alone may prove fatal to a complementarity challenge in many cases – possibly including in the cases against Netanyahu and Gallant. That is because even if Israeli prosecutors were to open proceedings against them regarding the events which are the subject of the ICC cases, they would need to use domestic offences and forms of participation which may not fully address all aspects of the conduct covered by the ICC cases, with the potential result that the domestic cases would not concern the “same conduct” as those before the ICC.” (Para. 10, Executive Summary)
“Additionally, to date there has been no (known) investigation or prosecution in Israel of a military or political leader at the level which is likely to be the focus of an ICC case. Israel argues that it applies robust criminal justice processes in both the military and civilian spheres, and points to investigations overseen by the military police and the Military Advocate General into alleged crimes perpetrated by members of the Israel Defense Forces (“IDF”). However, without exception, such investigations concern low-level soldiers accused of direct forms of perpetration which involved a violation of IDF orders or rules. Such cases are unlikely to ever be the focus of an ICC prosecution. Instead, the ICC is likely to pursue persons at a mid- or high- level in Israeli institutions, who are alleged to have committed crimes not in violation of IDF orders or policies, but rather through those orders or policies. Even if a narrow margin exists within which such persons and conduct are able to be prosecuted under Israeli penal law, we have not found evidence that this has occurred to date. Regardless of why that is the case, if there has been no activity at the domestic level which concerns the same person and substantially the same conduct as an ICC case, the latter remains admissible.” (Para. 11, Executive Summary)
“[M]ilitary investigations tend to focus on the violation of IDF policies, orders and rules of engagement, but almost never consider whether such policies, orders and rules of engagement may themselves be part of an international crime.“ (Para. 465, Legal Opinion)
“These factors lead us to consider it unlikely that Israel or an individual suspect in an ICC case will be able to overcome the activity hurdle.” (Para. 12, Executive Summary)
“Nonetheless, if the subject matter of a given ICC case is an offence in Israeli law, it is possible that Israel might initiate relevant domestic proceedings in the future, even if for no other reason than to render that ICC case inadmissible. There would be nothing improper in such action by Israel: complementarity is designed to encourage domestic proceedings. Accordingly, although to date there have been no Israeli domestic proceedings likely to displace an ICC case via complementarity, it remains possible that such proceedings could be brought in the future.” (Para. 13, Executive Summary)
“With this possibility in mind, we have also considered the factors which might be relevant in the second step of a complementarity assessment, if Israeli proceedings are able to meet the activity test.” (Para. 14, Executive Summary)
“Unwillingness… seems certain to be a live issue in any complementarity challenge in the Palestine Situation which passes the activity test. Unwillingness is defined in the ICC statute as occurring where domestic proceedings are undertaken with the purpose of shielding the suspect; or where the domestic proceedings are affected either by unjustified delay or by a lack of independence or impartiality which is inconsistent with an intent to bring the suspect to justice.” (Para. 16, Executive Summary)
“Here our conclusions are far more circumspect. This is not because we are convinced that the Israeli justice system operates fairly in cases of IDF crimes against Palestinians. Rather, we emphasise that establishing unwillingness before the ICC is challenging. While many factors are at play, we highlight three which we view as particularly significant:
(i) First, the primary type of “unwillingness”, shielding, requires proof that obstacles in the justice process have a specific purpose. This is very difficult to establish. The other types of unwillingness can be more easily proved and are therefore more likely to be applied in practice.
(ii) Secondly, when assessing domestic justice systems, ICC judges have applied a presumption of impartiality. This has the effect of muddying somewhat the principle that a party who raises domestic proceedings to challenge admissibility bears the burden of proof. In practice, the ICC will not readily conclude that national judicial actors are biased or unwilling.
(iii) Thirdly, what must be demonstrated to show unwillingness is not merely a generalised pattern of bias or other failings in the justice sector. Such evidence would suffice where complementarity is applied at the situation level to an investigation as a whole (for example in an article 18(2) process). However, where complementarity is dealt with in a specific case, the question is whether that case is affected by a lack of independence or impartiality. The point is a fine one. We do not say that material demonstrating systemic bias or structural failings cannot be relevant. To the contrary, ICC judges have accepted the relevance of material about the broader national justice section. However, such material is unlikely to be determinative on its own. The question will remain whether the particular case at hand has been tainted by those systemic failures.” (Para. 17, Executive Summary)
“Some commentators have suggested that Israel could establish a commission of inquiry which would meet the requirements of article 17 [of the Rome Statute]. In Section 8.2.2 below we consider whether Israeli commissions of inquiry might ever fulfil the “activity” requirement. However, for the reasons elaborated there, commissions of inquiry cannot overcome the fundamental obstacle of the conduct in question not being criminal under Israeli law. This obstacle means that there is no kind of legal process in Israel which could constitute a step towards criminal proceedings for the same conduct as the existing ICC case(s).” (Para. 318, Legal Opinion)
1Megan Hirst is a barrister at Doughty Street Chambers. She is the former International Civil Party Lead Co-Lawyer at the Extraordinary Chambers in the Courts of Cambodia and has represented victims in several proceedings before the ICC.
Nikila Kaushik is a barrister at Doughty Street Chambers. She was previously an associate lecturer at the University of Sydney and previously worked at the Extraordinary Chambers in the Courts of Cambodia and the ICC.