Williams, who says he legally uses marijuana to treat chronic pain caused by multiple sclerosis, was scheduled to stand trial in May on the charge. But a Milwaukee County judge dismissed the case at the district attorney's request after the pipe tested negative for the drug, the Milwaukee Journal Sentinel reported.
"We concluded that this case was not provable," Chief Deputy District Attorney Kent Lovern said.
Williams, who lives in New York, is participating in experimental treatment at the University of Wisconsin-Madison. He said he forgot the pipe was in his bag, and apologized for inconveniencing the airport security agents, deputies and court system. Williams said he is thankful that he can put the episode behind him.
The Associated Press contributed to this report.
