On Sunday, Jan. 5, President Trump—as he is wont to do when criticized—doubled down on his threat to bomb Iranian cultural sites if Iran attacks the United States in response to the killing of Qassem Soleimani.

Although the United States is not a party to the Rome Statute, which makes intentional attacks on historic monuments a war crime, the United States is a party to the 1954 Hague Convention on Protection of Cultural Property in the Event of Armed Conflict, which the Senate approved in September 2008, when I was legal adviser. The Bush administration strongly supported Senate approval of the treaty, and I testified in favor of it in April 2008, along with Defense Department Deputy General Counsel Chuck Allen and a senior Joint Chiefs of Staff military representative. The Bush administration supported ratification of the treaty because it reflected long-standing U.S. practice of not targeting cultural sites in wartime. I testified at the time that “we have concluded that U.S. practice is entirely consistent with this Convention and that ratifying it will cause no problems for the United States or for the conduct of U.S. military operations.”

I would like to think that when Secretary of State Mike Pompeo said on Sunday, in response to questions about the president’s threat to attack Iranian cultural sites, that “[e]very target that we strike will be a lawful target,” it is because he had been briefed by the lawyers in the Legal Adviser’s office on the requirements of the Hague Cultural Property Convention.

Secretary of Defense Mark Esper and Chairman of the Joint Chiefs of Staff Mark Milley should similarly affirm publicly that the United States will comply with its legal obligations during armed conflicts, and privately they—as well as White House Counsel Pat Cipollone, Attorney General William Barr and National Security Adviser Robert O’Brien—need to educate the president on U.S. legal obligations governing the use of military force. I urge the lawyers in the Departments of State, Defense, and Justice and the White House to make sure this happens.

As I said in my November 2016 Lloyd Cutler Rule of Law Lecture at the Supreme Court, Trump and Vice President Mike Pence should learn the domestic and international law rules that govern the use of military force and the conduct of military operations and to understand why they are important. I also noted the following: