Williams, a former Boston College player, was arrested by campus police after arriving to see the Eagles play Duke on Feb. 15. Williams had been served in May with a permanent no-trespassing order.
The Suffolk County district attorney dropped the case Thursday after getting a letter from Skinner saying he'd invited Williams to the game and was unaware of the no-trespass order.
Williams, who appeared in a Boston court on Thursday, refused to comment.
Williams was dismissed from the Boston College team in January 2007 for rules violations that included an arrest for marijuana possession in 2005. That charge was dropped after he completed a rehabilitation program.
He was the Nets' first-round draft pick in the 2007 NBA draft.
His lawyer, Howard Fisher, said Williams went to the BC campus at the "express invitation" of Skinner, who left a ticket for him for the BC-Duke game at the "will call" window.
Fisher said Williams' arrest was the result of "a lack of communication between the police department and the athletic department" of Boston College.
"It's an unfortunate situation. Mr. Williams has a strong affinity for Boston College and its basketball program," Fisher said. "I'm sure he feels he's happy to get this behind him and continue with his career."
Campus police would not say why the original no-trespassing order was issued against Williams. Jack Dunn, a spokesman for BC, also declined to comment, citing federal privacy laws that prohibit colleges from releasing academic or disciplinary records of students.
Assistant District Attorney Ellen Bisson said the college is willing to rescind the no-trespass order if Williams writes a letter to campus police requesting that it be dropped.