1) As of the Great Depression (approximately), it's understood the Fed's interstate commerce regulatory authority extends to intrastate commerce, on the grounds that the economy of one state impacts the economy of adjacent states---i.e. if Idaho discounts potato sales from Idahoans to Idahoans, and as a result depresses the potato demand from the farms of neighboring states, the Federal government can intervene on what is a completely Idaho-internal policy. It is under this theory that the Fed prohibits certain drugs (even if the drugs were manufactured and sold completely in-state).

2) Given that corporations exist only as a legal construct, I'm pretty certain that the government has a great deal of lattitude in what it can compel corporations to do or refrain from doing. It's worth noting that the US law also treats corporations as people; however, it does so because of the law itself (1 U.S.C. §1); modifications to that law can alter the nature of corporations in US law.