The U.S. Supreme Court invalidated a key provision of the 1965 Voting Rights Act in a ruling handed down Tuesday morning that will have far-reaching consequences for minority voters, perhaps for years to come.

The Voting Rights Act ensures that state and local governments do not enact measures that prevent racial minorities from voting, common practices during the Jim Crow era. Proponents of the Voting Rights Act claim many of those practices are still in effect, though in less overt guises.

At issue in this ruling is a preventative measure in Section 5 of the Act, called "preclearance," which requires jurisdictions with a history of voting discrimination to seek federal approval before enacting any changes in voting procedures. The Supreme Court did not strike down preclearance, but it did invalidate the formula laid out in Section 4 that determines which jurisdictions are subject to it.

"Section 4 of the Voting Rights Act is unconstitutional; its formula can no longer be used as a basis for subjecting jurisdictions to preclearance," wrote Chief Justice John Roberts in the 5-4 decision. Roberts goes on to say the preclearance requirement and the criteria that determined its application were necessary in 1965, but no longer.

"Nearly 50 years later, things have changed dramatically. Largely because of the Voting Rights Act, '[v]oter turnout and registration rates' in covered jurisdictions 'now approach parity. Blatantly discriminatory evasions of federal decrees are rare. And minority candidates hold office at unprecedented levels.'... In 1966, the coverage formula was 'rational in both practice and theory.'... Coverage today is based on decades-old data and eradicated practices... Congress based its coverage formula on that distinction. Today the Nation is no longer divided along those lines, yet the Voting Rights Act continues to treat it as if it were," Roberts wrote.

The Court ruled Congress could create another preclearance test based on more recent data, but with such a divided Congress, that is likely impossible. In essence, the ruling invalidates the Voting Rights Act, a law many consider to be the most important piece of civil rights legislation of the last 50 years.