What is the political/legal distinction between a "state" and a "commonwealth" in the United States?

Question

Some of the "states" in the United States are referred to as a Commonwealth rather than State (Virginia, Massachusetts, Kentucky and Pennsylvania specifically). The Wikipedia article for Commonwealth States indicates that there is no legal distinction between these states and other states and no differences in the rights enjoyed by citizens of these states.

However, an article I was reading today speaks of local law enforcement officers who are refusing to enforce any new federal gun laws that may be passed in response to the recent mass shootings around the country. In that article a local official in Kentucky was quoted as saying:

They need to go back and study that. We are a commonwealth. I can ask federal people to leave, they have to leave. I can ask state people to leave, they have to leave.

Nullification of federal laws by states has been tried and challenged in the Supreme Court (see the Civil War) before and subsequently ruled to be unconstitutional via the Supremacy Clause. Therefore, is there any justification to that statement due to Kentucky's status as a Commonwealth?

EDIT: Please do not focus on the constitutionality of any specific federal statute. The question is only asking for a legal difference between states and commonwealths as conflictingly referenced by Wikipedia and the article cited in the question. The origin of the law should be considered irrelevant.

Answer 1

Actually, in a Commonwealth (e.g. Puerto Rico), some Federal laws (e.g. taxes) don't apply, so in one way, the good Sheriff was right </obi-wan kenobi>.

A commonwealth is a

self-governing, autonomous political unit voluntarily associated with the United States, namely, Puerto Rico and the Northern Mariana Islands.

The problem is that none of the 4 US States (VA/KY/MA/PA) that officially call themselves "Commonwealth" are legally in a commonwealth status like Puerto Rico is, so overall he was wrong, since he's an officer in KY and not PR.

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Also, in the interest of clarity, that same official quoted in your question very explicitly stated that:

If it goes through Congress, if it becomes law, if it goes that way, yeah, I'd enforce the law.

He was making distinction between laws and "Executive Orders", and in no way was talking about "Nullification of federal laws by states" as you expressed it.

Arguably, the new EOs that establish gun control establish new law, which goes beyond constitutional authority (though the only authoritative answer on that would require SCOTUS):

the Supreme Court ruled in Youngstown Sheet & Tube Co. v. Sawyer, 343 US 579 (1952) that Executive Order 10340 from President Harry S. Truman placing all steel mills in the country under federal control was invalid because it attempted to make law, rather than clarify or act to further a law put forth by the Congress or the Constitution (src).

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A further point of interest - the concept of local law enforcement not cooperating with the Federales for political reasons is not new, nor is it some right-wing-nut invention. The idea was popularized (not sure about originated) by the concept of "Sanctuary cities", where standing immigration laws are not enforced.

Answer 2

The usage of the term commonwealth in the US differs slightly from that in other English-speaking nations. Practically speaking, state vs commonwealth is a distinction without a difference in the US. Rational-sounding arguments trying to imply there is a legal difference are almost certainly fallacious.

The distinctions pointed out in the other answer to this question are based on standing as a state vs. a territory or possession, which is a meaningful distinction. They have nothing to do with the fact they happen to call themselves commonwealths.

See Encyclopedia Britannica for further support.

Historically, the first government to self-designate as a commonwealth was the Commonwealth of England. This usage came into existence in 1649 as a replacement for a "kingdom" when King Charles the First was executed, after the Rump Parliament had passed legislation forbidding declaration of a new king. The word was derived from the late middle English noun commonweal.

Note: none of the four US states that call themselves commonwealths, nor Puerto Rico actually meet the qualifications to be a member of the Commonwealth of Nations. In fact, any state's ratification of the US constitution essentially prevents them from becoming qualified as Commonwealth of Nations members, who recognize Queen Elizabeth as head of state (not head of government.)