A judge could decide as early as today whether to dismiss a lawsuit filed by Constellation Energy Group that challenges the authority of energy regulators to investigate its deal to sell half its nuclear power assets to a French utility.

The legal battle between state officials and the company stems from the Maryland Public Service Commission's ruling last month that Constellation's $4.5 billion deal with Electricite de France must be in the public interest to go forward, thereby initiating a regulatory review.

Constellation, the parent of Baltimore Gas and Electric Co., the region's largest utility, filed a lawsuit in Baltimore Circuit Court seeking to overturn the PSC's ruling.

On Wednesday, state officials and Constellation argued their case before Judge Stuart R. Berger, who said he will try to issue a ruling by 5 p.m. today.

Joshua Auerbach, an assistant attorney general for Maryland, argued that the PSC's order is not final because the review process is ongoing; therefore, Constellation is premature in asking for relief from the court. He said Constellation and EDF will have ample opportunity for judicial review after the conclusion of PSC proceedings.

Attorneys for the PSC and the Office of the People's Counsel, whose office represents the interests of consumers in utility matters, argued in support of the state's motion.

Attorneys for Constellation and EDF argued that the PSC is expected to conclude its review too close to Sept. 17, which the parties say is the deadline for the transaction to be completed.

Deborah Jennings, an attorney representing Constellation, contended that the PSC does not have the authority to review the company's transaction with EDF, citing state law that allows state energy regulators to review transactions that involve at least 20 percent of the shares or control over more than one-fifth of board seats at the owner corporation.

EDF would own a 9 percent stake in Constellation stock and have one of 13 seats on the board, Jennings said.

In its order, the PSC came to the opposite conclusion about the state law because EDF would acquire Constellation assets, not voting interests.

The state law that spells out the threshold for regulatory review came as a result of a $2 billion settlement last year between the state and Constellation, which have had a contentious relationship for years because of rising electricity bills. The settlement also included consumer rebates, rate credits and other concessions.

"Now, they're challenging the very agreement they negotiated and signed," said Constellation spokesman Rob Gould. "We're defending our legal rights, which is what any business or individual would do under the circumstances."

An earlier version of this article misspelled Judge Stuart R. Berger's name. The Baltimore Sun regrets the error.