Steroids in Baseball

When did steroids become illegal in baseball? Our friend Adam thinks it was just recently that steroids became illegal. First of all much has been made of the recent changes in punishments for steroid abuse, but steroids have been illegal since the 1940's. I think America invented baseball and I think baseball, Major League at least, is mostly played in the United States. Steroids are a controlled substance, just like cocaine etc. They are a drug and they are illegal for United States citizens to use. I guess that means they are illegal in baseball. What do you think?
A-ron