The rule, approved last spring, prohibits players from lowering their helmets to initiate contact with an opponent. League officials said at the time that it would apply to all players at every position, and noted specifically that running backs who lowered their heads to bowl over defenders would be called. But through the first 13 weeks of the season, only defensive or special-teams players had been penalized.
The play occurred with 11 minutes, 32 seconds remaining in regulation of the Cowboys' overtime victory Sunday against the visiting Philadelphia Eagles. Elliott lowered his head and hit Eagles safety Corey Graham at the end of a 12-yard reception.
NFL owners approved the rule because internal research showed that contact between players with lowered helmets, and linear backs, increased the possibility of head and neck injuries.
"It applies to both offense and defense," referee Clete Blakeman said in a pool report after the game. "The ruling was basically that he lowered his head and initiated the contact against the defender with the helmet as it's defined in the rule book."
Asked how difficult the rule was to apply to Elliott's veer into the defender, considering the speed of the play, Blakeman said, "It's hard. It's a hard game and what we do is hard, but we feel good about the call. A couple of us, actually two of us, had it as the same foul from different angles."
After the penalty, Elliott was evaluated by medical personnel and missed five snaps before returning.
Elliott said he suffered a stinger on the play, not a concussion, but he was able to return after missing five snaps.
"I mean when you're on that sideline, I got to protect myself," Elliott said. "If the guy's going low, I got to go low too. The rules are for the betterment of the game, the rules are for our safety. If there was an illegal helmet-to-helmet contact, that's something I need to go look at and work on. It's not OK. I mean it's just a tough play."
Through the first 13 weeks of the season, there were a total of 10 flags for use of helmet.
ESPN's Todd Archer contributed to this report.