Hardy, who joined the Cowboys as a free agent this year, was notified Wednesday of the decision in a letter from Commissioner Roger Goodell. Hardy plans to appeal.
Goodell cited "sufficient credible evidence that Hardy engaged in conduct that violated NFL policies in multiple respects and with aggravating circumstances." His assault case had been dismissed in a North Carolina court, but an NFL investigation concluded that Hardy used physical force against Nicole Holder in at least four instances.
Hardy was on the commissioner's Exempt List last season and did not play for Carolina, although he was paid his $13.1 million salary.
Copyright 2015 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.