When it comes to discussing whether Israel's initial attack on Iran was justified or not, the arguments on both sides are strident and emotional.

Israel broke international law by attacking another country, one side says. It's a rogue state, bombing across borders with impunity, they claim.

But Israel has been threatened by Iran for years and Iran was on the verge of making a nuclear bomb, the other side argues. That poses an existential threat, they insist.

But which side does international law — unswayed by emotion — come down on?

How do analysts view legality of Israeli strikes?
Senior Israeli politicians described their country's attack on Iran on June 13 as a "preemptive, precise" attack on Iran's nuclear facilities, arguing it was self-defense because they feared a future nuclear attack by Iran.

Under international law, there are very specific rules about self-defense, for example Articles 2 and 51 of the United Nations Charter, and it's more likely this was what's known as a "preventive" attack.

"My impression is that the majority of legal analysts see [Israel's attack] as a case of 'prohibited self-defense'," Matthias Goldmann, a law professor and international law expert at EBS University Wiesbaden, told DW. "Because the requirements for self-defense are rather strict. They require an imminent attack that cannot be fended off in any other way. If you apply that requirement, you come to the conclusion that there was no attack imminent from Iran."

The timing alone makes that clear, Goldmann and others argue. On June 12, the International Atomic Energy Agency, or IAEA, issued a statement saying that Iran was not fully cooperating with it. But Israel has not presented any evidence as to why they believed a nuclear threat from Iran was so close and US intelligence suggests Iran was possibly three years away from a bomb.

There have been years of threatening rhetoric between Iran and Israel but it's deemed highly unlikely that Iran would fire a nuclear weapon at Israel later this month.

"Look back at the Cold War," Goldmann suggested. "Both sides had nuclear weapons and relied on the principle of mutually assured destruction — where you don't use your nuclear weapon because you know the counterstrike would be fatal. That's why the mere fact of possessing nuclear weapons in itself cannot be considered an imminent attack."

Israel itself already has an unspecified number of nuclear weapons but never signed the UN's Treaty on the Non-Proliferation of Nuclear Weapons and does not allow international inspections.

In defense of Israel
In a text for the website Just Security, Israeli law professors Amichai Cohen and Yuval Shany agree an attack in self-defense would have been illegal. But, they say, the attack on Iran should actually be seen as part of the larger conflict. "That changes the legal arguments because the attack would have happened in a differently defined context," they say.

In another opinion published this week on the US military academy West Point's website, Articles of War, Michael Schmitt, an American professor of public law, argues that the severity of the Iranian nuclear threat means the concept of self-defense could be interpreted more liberally.

But Schmitt admits this is a "tough case" because there were still other options than force. Another of the preconditions to attacking in self-defense is that a country must have exhausted all other options — and Schmitt notes nuclear negotiations between the US and Iran were ongoing at the time of the attack.

There's another reason why most legal experts believe Israel's attack was illegal, says Marko Milanovic, a professor of international law at the UK's University of Reading. Ultimately the law on this is built to be restrictive, he says. "It's about minimizing the need to resort to force. It's not about creating loopholes that any state that likes to bomb others can exploit," he told DW.

Laws of combat
"All is not fair in war, once the fighting starts," says Tom Dannenbaum, a professor of international law at the Fletcher School of Law and Diplomacy at Boston's Tufts University. "There is a carefully calibrated legal framework which applies equally to both sides."

Parties cannot target civilians or civilian objects, Dannenbaum told DW. "Objects only become military objectives when, by their nature, purpose, location, or use, they make an effective contribution to military action."

For example, this relates to Israeli targeting of Iranian nuclear scientists in their homes: Many lawyers explained that simply working on a weapons program doesn't make you a combatant.

Meanwhile, Iran's bombing has also killed civilians in Tel Aviv. "Even when targeting military objectives, parties must take all feasible precautions to minimize civilian harm," Dannenbaum explains, "and must not attack if expected civilian harm would be excessive in relation to anticipated military advantage."

It's hard to say if cases like this will ever be argued in court though. Goldmann, Dannenbaum and Milanovic say there's potential for related cases to eventually be heard at the International Court of Justice or perhaps at the European Court of Human Rights.

"But most of these types of issues on use of force don't end up in court," Milanovic said. "They get resolved in other ways. They're too political, or too large." Usually international diplomacy ends up resolving the issue, he noted.

Degrading international law
For many legal experts, one of the most worrying aspects is what appears to be implicit state support for Israel's most-likely-illegal definition of self-defense.

For example, while not referring specifically to the June 13 attack on Iran, statements by Germany's government have all contained some form of the phrase, "Israel has the right to defend itself."

"Of course, Israel does have a right to defend itself — but that right is limited by international law," Milanovic argues.

The rules on self-defense are strict for a reason, he and Goldmann explain. If you start expanding their definition — for instance, saying you have the right to attack another state because they attacked you several years ago, or might attack you a few years from now — the rules are eroded, along with the whole system of international law.

In the past, the international community has spoken out, for example, amid the controversy surrounding the US invasion of Iraq in 2003 based on claims that it possessed "weapons of mass destruction," Goldmann noted.

"The legal argument Russia made [for invading Ukraine] is also actually very similar to this Israeli argument," Milanovic pointed out. "If you read [Vladimir] Putin's speech on the eve of the 2022 invasion, it basically said that at some point in the future Ukraine and NATO are going to attack us and that's why we're doing this. But that's really not about self-defense," he concludes. "That's about, say, you don't like somebody, you think they're a threat and therefore you think you have the right to go to war with them. Which is simply not what international law says."