[Bubba Ho-Tep]

However, when the Federal government acts outside the bounds set for it by the constitution, it is acting illegally itself, and thus such laws are technically invalid.

And who decides that?

[rockrr]

Her feelings apparently.

[DeoVindiceSicSemperTyrannis]

And who decides that?

I think it is pretty clear cut in most all cases. But if it is not then the courts and the states have a right to judge. If the constitution does not give the federal government authority to do a certain thing, and the federal government does it anyway, I think it is pretty clear that the federal government is acting in an unconstitutional and therefore illegal manner (since the constitution is the supreme law of the land).