"Civilian control of our military is a fundamental principle of American democracy, and I will not vote for an exception to this rule," she says. | AP Photo Gillibrand says she won't vote for Mattis waiver

Sen. Kirsten Gillibrand (D-N.Y.) on Thursday said she plans to vote against the waiver required for retired Marine Gen. James Mattis to serve as Donald Trump’s defense secretary.

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.”

The law requiring a waiver for defense secretaries who have recently served in uniform dates to 1947, and Congress indicated that it did not expect exceptions to the rule after allowing retired Army Gen. George Marshall to lead the Pentagon under President Harry Truman in 1950. Because the waiver is legislative, it could ultimately prove subject to a 60-vote threshold for Senate approval — meaning that the GOP would have to secure at least eight Democratic votes in the upper chamber.

Gillibrand sits on the Armed Services committee, whose chairman, John McCain (R-Ariz.), hailed Mattis' imminent nomination and vowed to act on his confirmation "as soon as possible in the new Congress."

"America will be fortunate to have General Mattis in its service once again," McCain said in a statement Thursday.