The NFL doesn’t have final say on matters of discipline for on-field behavior, with either Derrick Brooks or James Thrash, jointly hired and paid by the NFL and the NFL Players Association, handling the appeal of any fines or suspensions. Sometimes, the league is willing to roll the dice on a suspension and accept the risk of losing on appeal.
http://profootballtalk.nbcsports.com/2015/12/21/suspension-possibility-looms-for-odell-beckham/