If Roger Clemens cheated, it is a matter for Major League Baseball to handle. If he broke the law, then a prosecutor should file charges. The role of the legislative branch is to write the law, not enforce it. A forklift driver who uses drugs has committed the same offense that Clemens is accused of.
Whatever one's opinion of the drug war, the primary responsibility of keeping employees drug free rests with the employers. Typically, when a private employer finds evidence of drug use, the suspected drug user is quietly terminated without involving the police. Congress doesn't grill factory workers over alleged meth use.
The burden of maintaining the integrity and reputation of professional sports rests with the leagues.