As President-Elect Donald Trump has made clear that he will choose former Marine General James Mattis for the job of Secretary of Defense, Mr. Trump will need the Congress to specifically waive a federal law that requires officers to wait seven years between active duty and taking the job as the Pentagon chief.
At issue here is 10 U.S. Code §113, which sets out the legal parameters for the Secretary of Defense - it includes that seven year waiting period - Mattis has only been retired since early 2013.
Congress would need to waive that provision - which has been done this once before - in 1950, when President Harry Truman selected Gen. George Marshall to be Secretary of Defense.
But there are already signs from one Democrat that might cause trouble:
Back in 1950, the debate over Marshall also stirred passions in the Senate, which took several days to finally approve the waiver and his nomination.
At the time, Senate Republicans denounced the idea of allowing Marshall to gain an exemption for the post of Defense Secretary; as one GOP Senator during debate labeled Marshall a "well-intentioned stooge."
This time, the party labels will be switched, as a Republican President seeks the exemption from the Congress, with Democrats playing the role of the opposition party.
As for Mattis, he is very well respected - it doesn't take long to find his supporters:
Back in 1950, after the Congress approved the legislation that gave Marshall an exemption, President Truman sent along the pen that he used to sign that bill into law.
(That letter was printed in Volume 7 of "The Papers of George Catlett Marshall.")
We'll see if President Trump gets to write a similar letter in 2017.