The Virginia Supreme Court upheld permits for construction of a multistate power line Thursday, rejecting a claim by the project's opponents that state regulators ceded too much authority to the federal government.

The court unanimously ruled that the State Corporation Commission's approval of the Virginia portion of the line was supported by evidence that the project is an acceptable solution to meeting future demand for electricity in northern Virginia.

Dominion Virginia Power and Trans-Allegheny Interstate Line Co., a subsidiary of Pennsylvania-based Allegheny Energy Inc., plan to build the 500-kilovolt transmission line from Washington County, Pa., to Loudoun County, Va. The 265-mile line would also cross northern West Virginia.

Opponents, including the Piedmont Environmental Council, the Power-Line Landowners Alliance and the Virginia counties of Fauquier, Prince William and Culpeper, claimed the SCC relied too heavily on results of the federal regulatory process as well as the "inherent bias" in data provided by the applicants.

They also claimed the process was titled to favor a transmission solution, and that the SCC should have given more consideration to generation or conservation alternatives. The court said the record in the case proves the opponents wrong.

"We agree with the Commission that the record as a whole demonstrates that the Commission fulfilled its statutory obligation to consider alternative solutions to the need for the proposed transmission line," Justice Lawrence L. Koontz Jr. wrote.

Robert Lazaro, spokesman for the Piedmont Environmental Council, called the ruling "an endorsement of business as usual" in Virginia, where utilities are accustomed to getting their way.

"The court said the utilities' experts are good enough for the SCC to consider, and if it's good enough for the SCC it's good enough for the Supreme Court," Lazaro said.

Dominion said in a written statement that it was pleased with the court's ruling.

"We presented evidence to the SCC which demonstrated a clear need for this project," Dominion said.

The utilities have said northern Virginia could face rolling blackouts by summer 2011 if the line is not built. Dominion also has said that electricity consumption downturns caused by a sour economy historically are followed by sharp increases when the economy rebounds, so the power grid must be ready to handle the eventual recovery.