Who rules on matters affecting the state's constitution?

The U.S. Supreme Court has original jurisdiction over all cases between two states. The most recent was <a class="url" target="_blank" rel="nofollow noreferrer" href="/to/?target=http://www.oyez.org/cases/2000-2009/2000/2000_130_orig">New Hampshire v. Maine</a> in 2001. The Supreme Court has another case-between-states, <i>South Carolina v. North Carolina</i>, scheduled for argument in October 2009.