CNN reports that Roh allegedly had machines to manufacture AR-15s in a warehouse outside Los Angeles. Customers could come to the warehouse and allegedly build their own rifles "for about $1,000."
Roh allegedly maintained his business, even after ATF officials warned him 'in person…that he was breaking the law."
Roh was eventually indicted, only to have federal authorities drop charges after prosecutors grew worried that a ruling in the case would be detrimental to the larger gun control system. They specifically worried the 1968 Gun Control Act could be endangered and that a trial might "seriously undermine the ATF's ability to trace and regulate firearms nationwide."
A trial to prosecute Roh would have brought attention to the fact that the ATF regulates AR-15s based not on the entire firearm, but on one part–the lower–which holds the trigger and hammer mechanism. The lower is like a command control center for firing bullets. Prosecutors feared the judgement in the case against Roh might somehow undermine the ATF's regulation, thereby rendering numerous gun controls moot.