For decades, leaders who were responsible for war crimes tended to plead ignorance or insist it was a mistake and their hands were clean. What has changed in the Middle East is the swaggering contempt we have seen from the United States, Israel and Iran as they instead dismiss, mock or flout the international laws protecting civilians. If the international community does not urgently reassert support for those norms, it may be acquiescing to their destruction.

US President Donald Trump, who told The New York Times he doesn’t “need international law” and the only restraint on his power was his “own morality”, and Defense Secretary Pete Hegseth, who has dismissed “tepid legality” in favour of “maximum lethality”, have expressed little regard publicly for the safety of civilians  affected by the US-Israeli war on Iran, which just entered its second month.

After announcing that the US had “demolished” Iran’s Kharg Island, Trump told NBC News, “We may hit it a few more times just for fun.” Hegseth has declared that “no quarter” would be given to enemies in Iran. That phrase indicates troops are free to kill those seeking to surrender rather than capture them. Such scenarios have served as a textbook example of a war crime in US military academies.

The Trump administration is not alone in this regard. In language eerily reminiscent of the war in Gaza, Israeli Defence Minister Israel Katz has threatened to demolish homes across southern Lebanon and block hundreds of thousands of civilians from returning.

Iran’s Islamic Revolutionary Guard Corps has declared US banks, investment firms and commercial ships valid targets despite their civilian status. Its spokesman warned Iranians that any street protests would be met with “an even harsher blow” than the January massacres, in which security forces killed thousands across the country. A state television presenter was more direct, saying opponents in the diaspora would face consequences that would see their “mothers sit in mourning”.

These statements are worthy of our attention not only because they telegraph a blatant disregard for civilian life but also because these leaders seem to mean it.

More than 2,000 people have been killed in Iran, more than 1,200 in Lebanon, and 17 in Israel. Altogether, several million people across the Gulf, Israel and Lebanon have been displaced or forced to flee from their homes. Based on a preliminary US military report, US forces were responsible for a deadly attack on an elementary school in Minab, Iran, in which more than 170 children and staff were killed.

The Israeli military has fired white phosphorus, which can burn to the bone, on Lebanese homes despite a clear prohibition on its use as a weapon in populated areas. Iran has launched internationally banned cluster munitions at Israeli cities and attacked commercial ships in the Strait of Hormuz.

The international legal system, designed to protect civilians during armed conflict, did not falter overnight. Unflinching US support for Israel as it carried out acts of genocide against the Palestinian population in Gaza, destroyed its hospitals and water systems, carried out countless air strikes that turned neighbourhoods into rubble and killed tens of thousands of Palestinian civilians over two and a half years contributed to a sense that some leaders would always be above the law.

Those double standards are alive and well, profoundly corroding respect for international law. When Iran struck Gulf energy infrastructure, condemnation rightly came within hours. But when Israel unlawfully dropped white phosphorus on Lebanese neighbourhoods, the same governments went quiet. Leaders need to say, with equal specificity and force, that attacks on Iranian power plants, Lebanese homes and Gulf civilian facilities are violations of the laws of war, regardless of who the perpetrator is. Otherwise, the rules are just a cudgel for punishing rivals.

The Geneva Conventions oblige every country not merely to follow the laws of war but also ensure global respect for them, including by refusing to arm forces credibly accused of violating them.

Yet arms continue to flow to belligerents on multiple sides of these conflicts with no apparent review of the likely impact. European governments that supply weapons or grant overflight and basing rights to forces unlawfully bombing civilians are not bystanders. If the actions of US and Israeli forces match the irresponsible rhetoric of their leaders, countries that arm or assist them could very well find themselves complicit in war crimes.

As during the war in the former Yugoslavia or more recently in Ukraine, the machinery of documentation and accountability needs to occur while the conflict is ongoing, not afterwards. Today, warring parties in the Middle East are working to prevent exactly that. Iran has imposed a nationwide internet shutdown and jailed people for sharing strike footage. Israel has banned live broadcasts and detained journalists. Gulf states have arrested citizens for posting images online. In the US, the Federal Communications Commission has threatened broadcasters’ licences over coverage of the war on Iran unfavourable to the Trump administration.

Governments with developed intelligence capabilities should be preserving and sharing evidence of war crimes right now: satellite imagery, communications intercepts, open-source footage. UN investigative bodies need immediate additional resources. And governments need to speak out clearly on the importance of justice for war crimes.

If this work waits until the shooting stops, the evidence may be gone, and the political will for accountability may quickly shift focus. The belligerents know it. They may even be counting on it.

The leaders repudiating the laws of war today may think they will gain from a world without rules, where brute force settles every question and all civilian harm is just written off as collateral damage. But by dismissing the principle of nonreciprocity, which makes clear that one side’s violations do not justify noncompliance by the other, they have spurred rounds of tit-for-tat strikes that put their own troops as well as their civilian populations in harm’s way.

Those who see the value of the existing system curbing the barbarity of war need to stand up for it. Otherwise, they may one day find themselves forced to explain to future generations why they did nothing while it burned.

The views expressed in this article are the author’s own and do not necessarily reflect Al Jazeera’s editorial stance.