A top Harvard constitutional law professor involved in a lawsuit seeking an injunction against Donald Trump’s declaration of a national emergency to fund a U.S.-Mexico border wall has thanked the president for helping to make the case.

On Thursday’s broadcast of “The Last Word with Lawrence O’Donnell,” the host asked Laurence Tribe if he’d “ever been on the opposite side of a litigant who was so helpful to your case in public comments that you could then simply type right into your brief to support your position?”

“Honestly, I have never had an opponent who was quite as helpful,” Tribe, who is representing the Texas county of El Paso in the case, said.

Tribe also thanked Trump “for being as obvious as he is about the absence of any emergency and about the fact that he is simply trying to do what emperors and kings do, not what a president of the United States should do.”

Check out the clip above.