The NFL on Tuesday said his return is conditional on staying out of legal trouble and "any prohibited alcohol-related conduct will likely result in an immediate suspension and potential banishment from the NFL."
The defensive lineman will be allowed to return to the Cowboys' facility starting in Week 7 for team meetings and individual workouts, the NFL said in a news release. Starting with Week 9, he can return to all team activities other than traveling with the team and playing.
"If Brent fully complies with these terms, and following an additional report and recommendation from the league's substance abuse program advisors, he will considered for full reinstatement to return to play following Week 10," the NFL's statement said. "Brent may appeal this decision within five days."
Brent also must fully comply with any evaluation, treatment or counseling required by medical or other professionals assigned to him and with the requirements set forth by courts regarding his probation, testing and monitoring, the NFL said.
Brent's agent, Peter Schaffer, said they would appeal the decision.
"We are going to invoke our appeal right," Schaffer said in a phone interview with ProFootballTalk.com. "We were truly hoping that the commissioner's response to Josh's request for reinstatement would be one that we wouldn't have to appeal, and that it would be fair and based on precedent. The last thing we thought we'd have to do today would be appeal the decision."
Schaffer pointed to the fact that Brent voluntarily retired.
"He could have forced the NFL to go through a tremendous amount of scrutiny for allowing him to play pending trial or for attempting to suspend him before he had been proven guilty," Schaffer told the website. "Where's the incentive for someone to do that in the future?"
Brent met with NFL commissioner Roger Goodell on Aug. 7 to seek reinstatement.
Because Brent retired a few days before the start of training camp in 2013, the Cowboys held his rights and activated him from the reserve/retired list.
On Dec. 7, 2012, Brent was involved in a car accident that killed best friend and teammate Jerry Brown in Irving, Texas. Brent was convicted of intoxication manslaughter and sentenced to six months in jail. He spent the final 45 days of his sentence at an alcohol and drug treatment center. He has been working out at Michael Johnson Performance in McKinney, Texas, since his release.
The Cowboys have expressed support for Brent since the accident, and team owner Jerry Jones consistently has said the team would welcome him back. Brown's mother, Stacey Jackson, has also supported Brent despite the accident, asking at her son's funeral for the team to help Brent in any way possible.
The Cowboys selected Brent in the seventh round of the 2010 supplemental draft. He played in 39 games, starting five, and developed into a solid nose tackle. The Cowboys have changed defensive schemes since Brent left the team, moving from the 3-4 to the 4-3, but the team continues to have a strong need for defensive line help.
"He has played at a level before that would help us, yes, and obviously we're trying to build this defensive line," Jones said earlier in training camp. "I know that one thing for sure, he is contrite, and I know he feels one of the best ways to pay his debt to what he feels to the family is to do what he does the best, and that is be a football player."
Brent has enlisted the help of former Cowboys Michael Irvin and Nate Newton, who also had off-the-field issues, to serve as mentors, along with adviser David Wells, who has a long history of working with troubled Cowboys, including Irvin, Newton, Adam Jones, and Dez Bryant.
"All you can do is give him support and try to direct him in the right way," Newton said during a visit to camp. "Let him know that what he's doing is a great thing and can only benefit him and the Cowboys alike. I'm a realist, man. Don't get caught up in, 'We love you.' Get caught up in, 'I've got a second chance. Do I love myself?' That's who you've got to love.
"If you love and respect yourself, then the Cowboys are going to benefit. If you don't love and respect yourself, the first person that's going down is you. For the Cowboys, you're just another story. Unfortunately, it can be a sad story. Or it can be a great story."
How quickly can Brent contribute? He has not been involved with football since the accident, although he did receive treatment for a time for his injuries immediately after the tragedy.
Cowboys coach Jason Garrett has said he does not think the scheme change would be too difficult for Brent to learn.
Teammates have said they would be happy to have Brent back with the team.
"I'll welcome him back with open arms," cornerback Morris Claiborne said. "I feel like everything happens for a reason. You never know what that reason may be. Everybody deserves a second chance. No matter what you've been through, you deserve a second chance. When he comes back, we're going to welcome him back with open arms."