I think it's iffy the government is stepping in on this one. The MLB franchises are not essential to daily living (for most normal people), and people will not be killed en-masse, lose their life savings, be permanantly disabled etc., by these cheaters.
OTOH, I guess I'm fairly into government oversight on these issues, but that's simply because I cannot trust people to do the morally right thing when their pocketbook is on the line. Frankly, in capitalism, the final morality is defined by the dollar.
But, my end answer is that, since no public would be directly hurt due to such behavior, it should be up to the industry and the fans to make the regulation of what's acceptable. We should be worry more about the dioxins that everyone inhales every day than about what people shoot into their own veins to be better at a sport.
***edit: About drug use in business: As long as your job doesn't have an immediate effect on the safety of others, I think the drug testing should be at the individual discretion of the company.