In the newest collective bargaining agreement between the NFL and Player's Union, marijuana was a critical topic. The Player's Union fought for a loosening of the rules governing players’ use of marijuana, and ultimately won. Under the new collective bargaining agreement, players who test positive for marijuana will no longer be suspended. Testing will be limited to the first two weeks of training camp instead of from April to August, and the threshold for the amount of THC needed to trigger a positive test will be raised fourfold. These changes are in line with marijuana policy changes in other sports leagues such as the NBA and MLB.
See "Marijuana Policies Headline NFL's New Labor Agreement ", Ken Belson, The New York Times, April 13, 2020