President Trump threatened to destroy 52 Iranian sites — “some at a very high level & important to Iran & the Iranian culture” — on Twitter on Saturday. This may seem like a small issue in the midst of an international crisis, but, as others have noted, his tweet amounts to an announcement of an intention to commit war crimes.

A part of the Hague Convention of 1907, signed over a century ago, says that “all necessary steps must be taken” to spare “buildings dedicated to religion, art, science, or charitable purposes, historic monuments, hospitals, and places where the sick and wounded are collected.” Similarly, the Geneva Convention Protocol I, signed in 1949 and amended in 1977, renders unlawful “any acts of hostility directed against the historic monuments, works of art or places of worship which constitute the cultural or spiritual heritage of peoples.”

Federal law in the United States says that violating these international conventions would constitute a war crime. Anyone who violates them could be imprisoned or, if death results from their actions, be sentenced to death. Members of the Trump administration should be on notice that they can be held liable under these provisions.