NFL commissioner Roger Goodell said Stallworth placed a "stain" on the reputation of the league and all its players.
Stallworth struck 59-year-old Mario Reyes on March 14 in Miami. He pleaded guilty June 16 to DUI manslaughter, a second-degree felony, and was suspended indefinitely by Goodell two days later.
Stallworth drew a 30-day jail sentence and reached an undisclosed financial settlement with the family of Reyes, who was leaving his crane operator job when he was struck.
In a letter to Stallworth released by the NFL, Goodell said he didn't take into account the sentence in determining the 28-year-old player violated the league's substances of abuse and personal conduct policies.
"Your conduct endangered yourself and others, leading to the death of an innocent man," Goodell wrote. "The NFL and NFL players must live with the stain that you have placed on their reputations."
Goodell held a hearing with Stallworth, his representatives and union officials Aug. 5. He also met privately with Stallworth on Monday at the player's request.
Police said Stallworth had spent the night drinking at a Miami Beach club and had a blood-alcohol level of .126, above Florida's .08 legal limit. Besides jail time, his sentence included two years of house arrest, eight years of probation and other restrictions.
A college star at Tennessee, Stallworth has also played for the New England Patriots, Philadelphia Eagles and New Orleans Saints. His first year with Cleveland was marred by injuries. He hurt his leg in training camp, which sidelined him for most of the season.
The Browns signed him to a seven-year, $35 million contract in 2008, hoping he could be a complementary No. 2 receiver and take pressure off Braylon Edwards. But Stallworth never got going because of the injury and made only seven starts. Edwards spent the season dropping important passes and Cleveland finished a disappointing 4-12.
Once it became apparent Stallworth could miss time, the Browns signed 12-year veteran David Patten and drafted Brian Robiskie and Mohammed Massaquoi in April to add depth at receiver.