The U.S. Supreme Court seemed ready on Monday to strike down the federal law that bans most states from licensing sports betting, though not by a unanimous vote.

Arguing in the case Christie v. NCAA, Gibson, Dunn & Crutcher partner Theodore Olson appeared to persuade several justices that the 1992 Professional and Amateur Sports Protection Act infringes on state sovereignty and amounts to “commandeering” states to do the federal government's bidding.

Olson acknowledged that the federal government may pre-empt state activities like allowing sports gambling under its powers to regulate commerce but, he asserted, only when it actually imposes a comprehensive regulatory scheme of its own that would render state actions inconsistent.

“PASPA is a direct command to the states without any effort to regulate sports wagering,” Olson told the justices. He added that the federal government wanted to “put the burden and expense and accountability all on the states.”

New Jersey Gov. Chris Christie, who has fought for years to overturn the federal law, watched the argument from the front row of the Supreme Court bar section.

A Seton Hall University School of Law graduate and former U.S. attorney, Christie joined the Supreme Court bar just before the argument began. Olson moved for Christie's admission, along with several other lawyers, and Chief Justice John Roberts Jr. said the motion was granted.

At a press conference after the argument, Christie predicted that “We're going to do well,” and Olson sounded optimistic as well.

Not a word was spoken—or a question asked—during the arguments about the potential consequences of striking down the law, namely the expansion of sports gambling across the nation. It is currently a mostly illegal activity that, according to the American Gaming Association, “has grown to a $150 billion-a-year industry.”

Association president Geoff Freeman said in a statement, “Today is a positive day for the millions of Americans seeking to legally wager on sporting events. … The justices of the Court expressed deep interest in the role of the federal government—a role that we believe has created a thriving illegal market that has driven trillions of dollars to offshore websites and corner bookies.”

Justice Elena Kagan pushed back against Olson's argument, asserting that a federal law that tells a state not to do something “sounds to me like the language of pre-emption,” which is permissible. Justice Sonia Sotomayor also seemed skeptical, but other justices appeared to accept Olson's formulation.

Paul Clement of Kirkland & Ellis rose to defend the law on behalf of the National Football League, National Basketball Association, Major League Baseball, the National Hockey League and the National Collegiate Athletic Association, and soon ran into obstacles.

“The citizens of the State of New Jersey are bound to obey a law that the state doesn't want but that the federal government compels the state to have,” Justice Anthony Kennedy said. “That seems like commandeering.”

Roberts asked Clement if Congress could forbid states to impose income taxes higher than 6 percent. When Clement said it was possible under court precedent, Roberts said that would “go to the fundamental powers and prerogatives of a state.”

Deputy Solicitor General Jeffrey Wall, also defending the law, said that Olson's assertion that federal law can pre-empt state law only when the federal government promulgates a comprehensive regulatory scheme is “a made-up principle.” But other justices did not pick up on the point.