Since the attacks of Oct. 7, every legal expert I have asked has shared one conclusion: Hamas’s attacks on civilians that day, including killing, torture, and hostage-taking, were war crimes. And because many hostages are still being held, that crime remains ongoing.

Tom Dannenbaum, a Tufts University professor, told me just days after the attack that there was “no question” Hamas’s attack had involved multiple war crimes. “Those are not close calls,” he said.

Since then, evidence has continued to mount. Last month, the prosecutor of the International Criminal Court announced that he was seeking warrants for the arrest of three Hamas leaders on charges of war crimes and crimes against humanity relating to the Oct. 7 attack on Israel, as well as the hostage-taking that followed. He also sought warrants for two Israeli officials. All of the subjects of the warrant requests have denied the accusations against them.

Last week, a U.N. commission concluded that there was credible evidence that members of Hamas and other armed Palestinian groups committed war crimes on Oct. 7, including by killing civilians, carrying out torture, and taking hostages. The commission also found evidence of Israeli war crimes, including the use of starvation of civilians as a weapon of war.

There are a lot of misperceptions about Hamas’s obligations under international law, so I thought I would use today’s column to explain those rules, how they apply to Hamas, and the surprising incentives they might create. Hamas declined to comment for this article but in past statements the group has claimed its fighters have a “religious and moral commitment” to avoid harm to civilians.

A quick note: I’m not going to write about Israel’s alleged war crimes in this post. I have written about a number of those issues previously however, including the use of starvation as a weapon of war, and the legal questions raised by the Israeli military’s attack on the World Central Kitchen aid convoy.