The Court ruled based on Federal Law. Federal Law trumps state laws which conflict, per the Constitution's supremacy clause.
This has nothing to do with the Supremacy Clause. The question is whether the federal government has the CONSTITUTIONAL AUTHORITY to regulare intrastate commerce. Despite the Constitution limiting the federal government to regulating commerce between the several state, the Court today, once again, rules that it includes commerce wholly within a state.
No, the Court based its opinion on a atrocious pro-New Deal case which expanded the interstate commerce clause to include just about anything.
That's pro New Deal court ruling.
The Constitution says that the States and the People have all power not granted to the federal government. A law that feds pass that is in conflict with the powers in the Constitution should be declared unconstitutional.