If an NFL team tries to call a timeout when it doesn't have one left, it will now be penalized for a delay of game, the 32 league owners decided during meetings on Tuesday. The rule was one of 19 proposed by various teams, as well as the NFL's competition committee.
Previously, a penalty was only called when teams called a faux timeout to freeze the kicker, netting a 15-yard unsportsmanlike conduct penalty. But there was nothing in the rulebook designed to prevent a team from calling a timeout and potentially stopping action without officially having a timeout remaining.
If a team called a timeout under the previous rules, referees would stop the game, have a discussion to determine if there was a timeout remaining and then announce over the stadium's speakers that the team in question did not, in fact, have a timeout. Meanwhile, play is stopped during this time.
This didn't happen often but there was one notable example last season during a Monday Night Football game. The Detroit Lions attempted to call a timeout when they had none remaining near the end of the first half against the New Orleans Saints. During the drive, the Saints scored three touchdowns that were all called back via penalties. The Lions went on to win, 35-27.
It's unclear if the Lions did it on purpose. But realizing the potential way this could be abused, the league has opted to make a change and if it ever happens in the future by accident or otherwise, the team calling the non-existent timeout will be penalized.