Gillibrand’s early opposition to the waiver came less than an hour after Trump announced he would tap Mattis for the Pentagon. The popular commander, nicknamed “Mad Dog,” is still expected to become the first defense secretary nominee in more than 60 years to win the congressional waiver that’s necessary to install him as the military’s civilian leader given his recent service in uniform.

“While I deeply respect General Mattis’s service, I will oppose a waiver,” Gillibrand said in a statement. “Civilian control of our military is a fundamental principle of American democracy, and I will not vote for an exception to this rule.”