The difference between a motorcycle club and a bike gang primarily involves the sorts of activities in which the groups participate. Regular motorcycle clubs are groups of individuals who share an interest in motorcycles and biker culture. Bike gangs, on the other hand, may share the outward appearance of regular motorcycle clubs, but these groups also engage in any manner of illegal activities from relatively minor offenses to serious organized crime.
While many motorcycle clubs and outlaw biker gangs share common iconography, such as leather jackets with elaborate embroidered patches, gangs use several patches and symbols that legitimate clubs do not. While patches that read "MC" originally just meant "motorcycle club," legitimate clubs rarely use this patch anymore, and it has become strongly associated with illicit biker gangs.
A patch popular with gangs is the "1%er" patch and its variants. The origin of the patch is an alleged quote by an American Motorcycle Association official made during the 1950s, which stated that 99 percent of motorcycle clubs obeyed the law, tacitly implying the remaining one percent did not. The modern AMA denies this origin story.
A simple, but not foolproof, way to distinguish between a motorcycle club and a biker gang is to find out whether that club is registered with a national motorcycling organization. National motorcycling organizations, such as the American Motorcycle Association in the United States, register official motorcycle clubs and require all member organizations to abide by all local laws and regulations.