When President Donald Trump exercises his power to pardon federal crimes, it’s usually to send a message. Last March, in an implicit jab at Hillary Clinton’s handling of classified information, he erased the conviction of former Navy sailor Kristian Saucier for photographing a submarine’s interior. The following April and May, while the Russia investigation loomed over him, he pardoned former Dick Cheney aide Scooter Libby and conservative filmmaker Dinesh D’Souza as a thinly veiled critique of federal prosecutorial overreach.

That makes his decision on Monday to pardon Michael Behenna all the more troubling. The former Army first lieutenant was convicted in 2009 for the murder of Ali Mansur, an Iraqi who Behenna killed after detaining and interrogating him without authorization. Behenna was sentenced to 25 years in prison, later reduced to 15 years, and was paroled in 2014. The White House cited the support of retired military officers and Oklahoma elected officials, as well as Behenna’s reputation as a “model prisoner,” when announcing the president’s act of clemency.

There is no legal or constitutional error in Trump’s decision to pardon Behenna. But it marks another troubling intervention by the president in the military’s efforts to punish war crimes allegedly committed by American soldiers. Taken together, these moves could send a disturbing signal to U.S. military personnel serving overseas: If you violate the laws of war, the commander-in-chief may well bail you out—especially if your case wins the sympathy of Fox News.

The American Civil Liberties Union, one of Trump’s most persistent foes, said the pardon amounted to a “presidential endorsement” of Behenna’s crime. “The military appeals court found Behenna disobeyed orders, became the aggressor against his prisoner, and had no justification for killing a naked, unarmed Iraqi man in the desert, away from an actual battlefield,” Hina Shamsi, the ACLU’s national security project director, said in a statement. “Trump, as commander in chief, and top military leaders should prevent war crimes, not endorse or excuse them.”

Trump, for his part, has never been an enthusiastic proponent of the laws of war. On the campaign trail, he declared that “torture works” and supported waterboarding, complained that the Obama administration was fighting a “politically correct war” against the Islamic State, and suggested that he would order U.S. forces to kill suspected terrorists’ family members. “You have to take out their families, when you get these terrorists, you have to take out their families,” he said in an interview in 2015. “They care about their lives, don’t kid yourself. When they say they don’t care about their lives, you have to take out their families.”