The 10-year labor agreement between the N.F.L. and players union that was ratified on March 15 is filled with dozens of incremental changes, most notably the one-percentage-point increase in the share of league revenue that the players will receive.

One of the biggest overhauls in the agreement, though, was a change the league had long resisted: loosening the rules governing players’ use of marijuana.

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 9-delta tetrahydrocannabinol — or THC, the psychoactive compound in marijuana — needed to trigger a positive test will be raised fourfold.

In adopting the changes, the N.F.L., a league not known for its liberal views, caught up to and in some ways leapfrogged Major League Baseball, the N.B.A. and other leagues that had already eased their rules as acceptance of marijuana became more common in many parts of the country.