In preparation for the 2015-16 season, NFL Football Operations issued a reminder to general managers, head coaches and equipment managers that all players must be in compliance with the league rule on mandatory thigh and knee padding. The league emphasizes this rule every season as part of its efforts to protect players from unnecessary risk and ensure that the game is presented in a professional manner consistent with NFL standards.
NFL uniform inspectors will be on the field before every game to inspect players and make sure that they present a professional and appropriate appearance on game-day. The uniform inspectors also will have access to the sidelines after kickoff and will continue to inspect players to confirm that they are wearing the mandatory equipment.
The rule states:
Rule 5, Section 4, Article 3. All players must wear the equipment and uniform apparel listed below, which must be of a suitably protective nature, must be designed and produced by a professional manufacturer, and must not be cut, reduced in size, or otherwise altered unless for medical reasons approved in advance by the Commissioner. During pregame team warm-ups, players may omit certain protective equipment at their option, except that helmets, shoulder pads, thigh pads, and knee pads must be worn.
Read more about NFL Rules Enforcement.
Any player who is not wearing his uniform in compliance with guidelines set by the rule will not be permitted to enter the game. If a player refuses to make changes to his uniform to comply with the rule and tries to enter the game, the uniform inspector will notify the team equipment designee, on field equipment manager, the designated league observer/supervisor and sideline game official of the player’s non-compliance.
Players violating the uniform policy are subject to being removed from the game until the violation is corrected.