Commonwealth Court Judge Robert Simpson delivered the decision just five weeks before the November 6th presidential election.
The law requires each voter to show a valid photo ID at the polls.
Judge Simpson ordered the state not to enforce the photo ID requirement in this year's election, but will allow it to go into effect next year.
Today's decision may be appealed to the State Supreme Court.
Democrats believed the voter ID requirement was a ploy to defeat President Obama.
Other opponents argued it would prevent the elderly and minorities from voting.
The law's supporters meantime, say they fear election fraud.