However, if a state like New Hampshire were to pass a law such as the Firearms Freedom Act with no intention of enforcing it, or of defending NH citizens against illegal federal attempts to ignore the FFA, of what good is the measure? It quickly becomes, like current Supreme Court interpretation of the Tenth Amendment itself, simply a toothless "truism" that can be discarded at will by federal courts.

To avoid simply being overruled or rendered moot by more tortured ignorance of the Supremacy Clause, the states must take some sort of a stand in defense of their sovereignty measures. Whether that involves police power or the power of the purse is up to them.

In the long run, as Patrick also mentioned at TNR, effective enforcement could potentially be achieved through fiscal means such as the withholding of federal income taxes by the states subject to constitutional review of federal activities. But, as this is the age of entitlement, I am inclined to think that public opinion would judge more harshly a state that started out by denying the feds the money they need to write welfare checks than one that simply enforced its own laws using its rightful police powers.