The NFL initially suspended Hardy in April for what it deemed to be multiple violations of the league's personal conduct policy during an incident with a former girlfriend in spring 2014. The charges against Hardy, who was with the Carolina Panthers at the time, were eventually dismissed after the ex-girlfriend, Nicole Holder, refused to cooperate with the Mecklenburg (North Carolina) County district attorney's office.
"After consideration of all the record evidence and arguments, I conclude that the Commissioner acted within his authority and properly exercised his discretion in finding that Hardy violated the NFL Personal Conduct Policy," Henderson said in a statement. " . . . I find that the conduct of Hardy clearly violated the letter and spirit of any version of the PCP since its inception, and of the NFL Constitution and Bylaws long before then. The egregious conduct exhibited here is indefensible in the NFL.
"However, ten games is simply too much, in my view, of an increase over prior cases without notice such as was done last year, when the 'baseline' for discipline in domestic violence or sexual assault cases was announced as a six-game suspension."
In July 2014, Hardy was found guilty by a judge of assaulting Holder and threatening to kill her. He received a 60-day suspended sentence and 18 months' probation on misdemeanor charges but appealed the judge's ruling in favor of a jury trial. The case was dismissed in February when Holder chose not to cooperate with authorities after receiving a settlement from Hardy.
Like law enforcement, the NFL was unable to interview Holder but was provided with photos and other materials for its independent investigation that concluded Hardy used physical force against Holder in "at least four instances."
The league also said Hardy failed to provide complete and accurate information to NFL investigators and staff and that Hardy's attorneys did not provide a copy of the settlement with Holder or acknowledge that an agreement exists.
In its appeal, the NFL Players Association believed commissioner Roger Goodell used the personal conduct policy to penalize Hardy even though the incident happened before the policy was in place.
"We are looking forward to the start of the season and having Greg be a part of the team," Cowboys owner Jerry Jones said in a statement Friday.
In response to the reduction of Hardy's suspension, National Organization for Women president Terry O'Neill said the NFL should be more concerned about changing its culture.
"What's very, very sad is that nothing has come out of the NFL that indicates a real commitment to ending the violence against women problem that they have in the NFL," O'Neill said. "... The only thing that comes out of the leadership of the NFL is the owner of the Dallas Cowboys is thrilled to have a talented athlete on the field and says nothing about the victim of the domestic violence. I think that, it's very sad to me. It's pushing football way down the wrong path."
Drew Rosenhaus, Hardy's agent, said he will confer with Hardy, the NFLPA and his lawyers to discuss their next move.
"Still considering further legal action," Rosenhaus said.
When the Cowboys signed Hardy to a one-year deal in March, the team knew he faced a possible lengthy suspension but structured the contract in such a way that it did not include any guaranteed money and the biggest payment would come in the form of per-game roster bonuses.
Hardy's deal is worth up to $13.2 million, but he will earn as much as $9.5 million by being on the 53-man roster. He has earned a $1.3 million workout bonus this spring and is scheduled to make a $750,000 base salary. He can also earn up to $1.804 million in incentives.
He missed all but one game last season with the Panthers but was paid his $13 million salary while on Goodell's exempt list.
Jerry Jones, executive vice president Stephen Jones, coaches and players have lauded Hardy's offseason, calling him one of the hardest workers on the team.
Hardy will be permitted to take part in training camp and preseason games. The suspension will begin Sept. 5.
Information from ESPN's Tania Ganguli and The Associated Press contributed to this report.