These laws do no more than point out federal overreach and state that the state will not comply. Some of them actually go so far as to criminalize federal LEO's for enforcing federal laws on guns to which they do not properly apply. Next step would be for the state saying its state LEO's will protect with force of arms any citizen of the state the feds want to prosecute for a "violation" of a federal law lacking jurisdiction. And mean it. There are I think 8 states that have passed some version of this, and so far only Wyoming's contains the prohibition of federal agents (Vermont's or New Hampshire's did too, but failed to be passed), but there have been no confrontations as yet, so it remains to be seen how serious the states were or if it was just symbolism.
See Texas HB553 which is introduced in this legislature. This is just such a bill for Texas.
How about also specifying that attempts to enforce illegal federal statutes may be prosecuted under existing state laws against robbery, kidnapping, etc., and further specifying that since such illegitimate enforcement can by definition form no part of a federal official's legitimate duties, any statute which would seek to remand such prosecution to federal court shall be deemed inapplicable?