system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the Nullification Crisis?

I searched for other posts like this but the one that I found had commenters making fun of the OP for “not doing his own APUSH homework”. In case anyone wanted to say the same thing to me, I’m only asking because I didn’t pay attention when I was learning about it in high school and I don’t understand all the legal and political jargon on the Wikipedia page.
gpt
Basically one state (South Carolina) tried to declare a federal law (the Tariff of 1828, and later the Tariff of 1832) nullified with respect to that one state.  In other words, SC asserted that it could declare the tariff law invalid and unenforceable in SC only, and would not have to bother establishing it was unconstitutional generally (as to other states).   There were supporters of this approach at the highest levels of the federal government, and SC was preparing to take military action to support its view (recall that military power resided in the state militias at the time), and the federal government passed a law allowing the use of force against SC, all of which which would have led to an armed conflict between SC and the federal government 20 years before the Civil War.  The crisis was resolved before shots were fired when a new tariff bill was passed that was acceptable to SC, and the state withdrew its declaration of nullification.  The issue is important because it involves the balance of power between the states and the federal government, which looked very different in the early 1800's as it does now.