The Baltimore native spoke Monday at a news conference with Maryland lawmakers who support legalized medical marijuana.
Williams, 54, was diagnosed with multiple sclerosis in 1990. He says he has been living with pain in his lower extremities, face and side for years and adds marijuana provides the only relief he can find.
When questioned by The Associated Press, he declined to comment about just where he obtains the drug.
The Maryland Senate passed a bill last year to allow physician-approved use of marijuana. The House didn't pass the measure but lawmakers say they'll try again this year.