Peter Jenkins, former UK representative at the IAEA, whom I "interviewed" once along with Farid Marjai, has this to say:
One of the most depressing aspects of all the talk about Israel or the United States destroying Iran's nuclear facilities (and much else besides, no doubt) is the near absence of any reference to international law. Even so distinguished an expert as Anthony Cordesman seems to take it for granted that there will be no legal impediment to the US attacking Iran if a credible threat of an attack fails to intimidate Iran into making the concessions required to pacify Israel.
Law professor Dan Joyner and others have also pointed out that attacking Iran would be contrary to international law. I should point out here that even threatening or planning such a war against Iran is itself a crime under international law, for which people have been hanged in the past. In other words the US and Israeli officials who have mouthed threats of attacking Iran are already war criminals. In fact US military personnel are obligated to ignore orders to attack Iran. But as a writer at the Guardian points out,
The legal niceties are unlikely to stop the US or Israel if they are determined to attack Iran. The Bush and Obama administrations both shopped around within their own legal departments until they got the advice they wanted to hear on issues from invading Iraq to the growing government surveillance of ordinary Americans.
Jenkins goes on to cite classical literature about the Peloponnesian war, where the weaker Melesians stood up to the expansionist Athenians. According to Thucydides, at one point in the dialogue between the representatives of Melos and the Athenians, the Athenian delegates said plainly: "You know as well as we do that justice is only at issue between equals in power; the strong do what they can and the weak suffer what they must." Boy isn't THAT a good description of the US attitude towards international law. John Bolton would have agreed.
I think the Iranian side is well aware that they can't rely on international law. After all it was Rafsanjani himself, commenting on illegal US support for Saddam's war of aggression against Iran including his use of chemical weapons against civilians at places such as Sardasht, who said that the war taught Iranians "that international laws are only drops of ink on paper"