Of course it is. The federal government wants to be supreme, and will never brook for dissent against it. You don’t actually believe that the Supreme Court always makes decisions that are constitutional do you? I mean look at Rove vs. Wade. The Federal government only cares about its own power.
What's that got to do with anything? FTR: no, I don't believe that every decision SCOTUS makes is necessarily constitutional. But they're still the law. You do believe in the law, don't you? Dred Scott v. Sandford was one of the poorest decisions ever handed down, but it was still law. Roe v. Wade is crap but we're stuck with it until we can build a super-majority.
Well, yes, by definition they are. People might believe them wrong, and the court may reverse itself from time to time, but whatever the court says is constitutional is constitutional because the Constitution gives them that authority.