The Repeal Amendment should not be confused with the power to "nullify" unconstitutional laws possessed by federal courts. Unlike nullification, a repeal power allows two-thirds of the states to reject a federal law for policy reasons that are irrelevant to constitutional concerns. In this sense, a state repeal power is more like the president's veto power.
This amendment reflects confidence in the collective wisdom of the men and women from diverse backgrounds, and elected by diverse constituencies, who comprise the modern legislatures of two-thirds of the states. Put another way, it allows thousands of democratically elected representatives outside the Beltway to check the will of 535 elected representatives in Washington, D.C.
Congress could re-enact a repealed measure if it really feels that two-thirds of state legislatures are out of touch with popular entiment. And congressional re-enactment would require merely a simple majority. In effect, with repeal power the states could force Congress to take a second look at a controversial law.