The Family Ties actor was arrested in Boulder, Colorado and appeared in court on Friday (19Feb10).
His defence attorney told the court the actor needs marijuana for headaches and has applied for a medical marijuana card.
Bonsall, 28, also pleaded not guilty to an assault charge and a failure to report charge involving another case.
He is accused of repeatedly hitting a friend in the head with a broken stool in December (09) and of missing a court hearing in 2007 in another assault case.
Bail was set at $10,000 (GBP6,250), according to U.S. TV news show The Insider.