The issue of old maps arose after the Pennsylvania Supreme Court rejected a plan that would have brought maps up to date to reflect the 2010 Census.
The state court said the plan by a Legislative Reapportionment Commission - criticized by Democrats as heavily gerrymandered - did not pass state constitutional muster. It said the plan improperly broke up counties and municipalities that should have been in single legislative districts unless "absolutely necessary."
The decision Wednesday came from Judge R. Barclay Surrick in U.S. District Court.
He rejected a request from Senate Majority Leader Dominic Pileggi, House Speaker Sam Smith and House Majority Leader Mike Turzai, among others, to issue a temporary retraining order against the old maps.
"Granting a temporary restraining order at this stage will delay the primary election and potentially disenfranchise Pennsylvania voters," Surrick wrote in an opinion.
"To enjoin the 2012 election from proceeding under the 2001 plan would leave the Pennsylvania primary in a state of unacceptable uncertainty," he said.
Surrick also refused their request to convene a three-judge panel for a further look at the case.
Contact staff writer Tom Infield at 610-313-8205 or tinfield@phillynews.com.