In your own words, describe the doctrine of nullification.

Nullification by definition is "the act of eliminating or cancelling something." In regards to history,  it is a legal theory that gave U.S states the power and privilege to "nullify" any federal law that the states considered to be unconstitutional. The Courts at the state and federal level  however  rejected the theory as they believed that the federal law stands superior to the state law. To this extend, the federal judiciary has the final authority to interpret the U.S constitution and federal law, not the State.

Their solution was to tax the colonists.