Oakland Raiders wide receivers Keelan Doss, left, and Antonio Brown warm up during minicamp on June 11 in Alameda, Calif. (AP file photo)

The arbitrator issued the ruling after holding a Friday hearing with Brown, representatives from the league and the players’ union.

“While I disagree with the arbitrator’s decision, I’m working on getting back to full health and looking forward to rejoining my teammates on the field,” Brown said in a statement on Twitter. “I’m excited about this season and appreciate all the concerns about my feet.”

Brown has not participated in a full practice for the Raiders after starting training camp on the non-football injury list with injuries to his feet that reportedly came from frostbite suffered while getting cryotherapy treatment in France. Brown was cleared to practice on July 28 and participated in parts of two sessions but wasn’t around the team last week when he had the grievance hearing with the NFL over his helmet.

NFL spokesman Brian McCarthy earlier in the day reiterated the league’s stance that Brown wouldn’t be allowed to practice or play without a certified helmet.

Oakland Raiders wide receiver Antonio Brown warms up during a team activity at the team's headquarters in Alameda, Calif., on May 28. (AP file photo)

“The player can’t practice or play in games with equipment that’s not approved,” McCarthy wrote.

The National Operating Committee on Standards for Athletic Equipment sets performance and test standards for equipment.

Brown’s Schutt Air Advantage helmet is no longer allowed because the NFL follows the National Athletic Equipment Reconditioners Association rule that helmets 10 years or older cannot be recertified.

Schutt discontinued making the helmet three years ago because current technology had moved past it, according to the company.