Acrisis erupted in the 1830s over the idea that a state could declare federal legislation invalid, prevent its enforcement, and possibly separate from the union. what word describes this idea?

The Nullification Crisis

Explanation:

During the administration of President Andrew Jackson erupted The Nullification Crisis  between 1832–33 turning into a political major issue. The Nullification Crisis involved a confrontation between the state of South Carolina and the federal government. An anonymous publication called  “South Carolina Exposition and Protest,” was released with the intention of posing the "Theory of nullification":

—the declaration of a federal law as null also voiding within state limits. It was argued that since the authority of the federal government was derived from the consent of the states, such states could nullify any federal law they considered unconstitutional.

Nullification

Explanation:

The theory of nullification was preached by Thomas Jefferson and James Madison. The states were said to have the authority given to them to be able to ascertain when the federal government goes beyond the powers they have and the states could term such acts as ‘void and of no force’ when it happens in their jurisdiction. When crises started between south Carolina and the federal government, a resolution was reached which nullifies the issue around federal tariffs in favor of the federal government and that weakened the theory of nullification.  

protected civil liberties and outlawed slavery in the new territories.