The memo says that violations of the league's personal conduct policy "regarding assault, battery, domestic violence and sexual assault that involve physical force will be subject to enhanced discipline."
The NFL Players Association said it had been informed of the increased punishments.
"As we do in all disciplinary matters, if we believe that players' due process rights are infringed upon during the course of discipline, we will assert and defend our members' rights," the union statement said.
The personal conduct policy is not subject to collective bargaining with the players' union, and the commissioner has leeway to impose punishments for such off-field violations.
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An initial domestic violence offense will draw a six-week ban without pay, although the memo says "more severe discipline will be imposed if there are aggravating circumstances such as the presence or use of a weapon, choking, repeated striking, or when the act is committed against a pregnant woman or in the presence of a child."
A second offense will result in banishment from the league, but a player will be allowed to petition for reinstatement after a year.
"There is no assurance that the petition will be granted," the memo says.
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The punishment for Rice drew plenty of attention, including from Congress. Numerous groups that advocate for women and families criticized the penalty as too lenient.
Rice's suspension begins Saturday, about six months after grainy video showed him dragging his then-fiancee off a casino elevator. Rice has never said exactly what happened in the elevator; he has said his actions were "totally inexcusable."
"My disciplinary decision led the public to question our sincerity, our commitment, and whether we understood the toll that domestic violence inflicts on so many families. I take responsibility both for the decision and for ensuring that our actions in the future properly reflect our values," Goodell wrote. "I didn't get it right. Simply put, we have to do better. And we will."
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Goodell's letter notes other steps the league will take to "strengthen our policies on domestic violence and sexual assault," including efforts to educate all NFL employees on the subject.
—By The Associated Press