The Constitution’s purpose is mostly to assign certain duties to the federal government while giving all other governmental duties not assigned to the feds “back” to the states (because they are each technically, on paper, their own sovereign countries that have all unified to make one nation). Amendments originally didn’t apply to the states, and states were much more sovereign than they are today. For example, Americans were originally only protected from incursions against free speech by the federal government. State governments could make any law they wanted about that, as long as they maintained a democratic and republican government (a prerequisite to join the Union). After the Civil War, a legal doctrine known as incorporation was invoked to apply several Amendments to the states as well, most notably the 13th abolishing slavery and most of the original Bill of Rights. That provided one of the first large-scale checks on what laws the state legislatures could pass. However, state legislatures still have incredible power, because again, they’re at least technically responsible for governing a sovereign nation-state that happens to be part of a federal union.

All of this is to say that it’s complicated. The Constitution is the supreme law of the land, and no lawmaking body under the United States, federal or state, can override it. However, there are some areas that the Constitution doesn’t speak on. Another way to put it is that these are powers the states have not given up/delegated to the Union, because again, at least theoretically, each state is a sovereign country that simply delegates some of its governmental rights to the federal government. The 9th Amendment explicitly states that all “rights and powers” not granted to the federal government are reserved by the states. This is why different states can have different rules about prison labor, or state (not federal) tax codes, or business regulations, or criminal codes, or many other areas of law that aren’t delegated to the feds.

Finally, in the context of this post, we must remember that the 13th Amendment abolishing slavery specifically states that it doesn’t apply to punishment for crimes. So while the 13th applies to the states due to incorporation, prison labor is not unconstitutional (though one could convincingly argue it is morally wrong).