Stephen Burbank ruled Tuesday in favor of the league and dismissed the grievances by both teams. The Redskins lost $36 million over two years. The Cowboys lost $10 million for overloading contracts during the uncapped 2010 season despite league warnings about such maneuvering.
The Cowboys and Redskins, who filed their grievances against the league and players' association, said in a joint statement they would "abide by the arbitrator's decision to dismiss."
"We will continue to focus on our football teams and the 2012 season," the NFC rivals said.
Cowboys owner Jerry Jones compared the dynamics of the salary cap with using a credit card.
"The way you work around the salary cap is you kind of use the credit card to spend money that you won't be spending in the future," Jones said Tuesday at the owners meeting. "So it caused us to do more credit card spending in the future."
Redskins general manager Bruce Allen said the team is "obviously disappointed." Asked how losing another $18 million might inhibit the Redskins, he said: "We'll see. We'll have time to talk about it."