Attached is his listing in the 1948 Army and Air Force Register. It shows him as a 2nd Lt in the Army Infantry Reserve in Oct , 1938 and honorably discharged 13 Sept, 1940. Of the many online bios, these mention those facts.
http://www.veterantributes.org/Tribu...p?recordID=288
http://acesofww2.com/USA/aces/blakeslee/
Note it appears he enlisted at Windsor in August, 1940. According to a recorded interview on YouTube, I think he flew up to Detroit, went to Windsor Canada to enlist and then went home to await the RCAF call-up. He then was discharged in September after he had been accepted in the RCAF.