Special master Stephen Burbank dismissed the teams' appeal of the league's finding they piled money into the uncapped season of 2010 by front-loading contracts.
As a result, the Redskins were hit with a cap reduction of $36 million over two years, while the Cowboys lost $10 million in cap space over the same time frame.
"We pursued our salary cap claim pursuant to the CBA and we respect and will abide by the arbitrator's decision to dismiss," the Cowboys and Redskins said in a joint statement. "We will continue to focus on our football teams and the 2012 season."
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