WASHINGTON — Supreme Court justices exchanged conflicting viewpoints Monday on whether Amtrak had the legal authority to help craft federal regulations over the use of railroad tracks.

The court heard arguments over a 2008 law that directed Amtrak to work with government agencies to develop new standards for improving the passenger railroad's on-time performance.

The American Association of Railroads, which represents the freight railroad industry, says it's unconstitutional for Congress to give a private company the power to create regulations. The industry objects to some of the new standards that allow Amtrak to keep its priority over freight trains that share common railroad tracks.

The Obama administration argues that Amtrak simply worked with the Federal Railroad Administration to devise the rules and, at any rate, the government retained ultimate control over how they were approved. The government is appealing a decision from the U.S. Court of Appeals for the D.C. Circuit which sided with the freight railroads.

Congress created Amtrak in 1970 as a for-profit corporation. Amtrak is not a government agency, but it's subject to government oversight, receives billions of dollars in federal subsidies and its board is nominated by the president.

Chief Justice John Roberts seemed concerned that the regulations could help Amtrak force proceedings in which freight railroads would have to defend their use of railroad tracks. Roberts said that sounds like "significant regulatory impact."

Under the regulations, if on-time passenger train performance averages less than 80 percent for two consecutive quarters, the federal Surface Transportation Board may investigate whether freight railroads caused the delays. Freight railroads could have to pay damages to Amtrak.

"It seems kind of regulatory," Justice Elena Kagan said of Amtrak's role.

Justice Department lawyer Curtis Gannon said Congress merely wanted to enforce violations of existing law that guarantee a preference to passenger railroads.

"The metrics and standards just cabin the circumstances in which Amtrak can seek that kind of enforcement," Gannon said.

Justice Stephen Breyer worried that a ruling against Amtrak could have drastic implications for other industries in which the government allows private companies to set compliance standards. He cited regulation of Internet domain names by the non-profit Internet Corporation for Assigned Names and Numbers — or ICANN — which is overseen by the Commerce Department.

"Once we go down that road, there is no stopping place," Breyer said.

Thomas Dupree, attorney for the freight railroads, said in the Internet context, "that's not a situation where you have a company trying to regulate other competitors in the market."

Justice Antonin Scalia noted that as soon as the regulations were issued "the on-time record of Amtrak went way, way up. So they had a very immediate and clear effect on the behavior or the parties."

"So long as it is operating on a for-profit basis and is given the last word on some regulatory matters that disadvantage its competitors, there's a violation of due process," Scalia said.

The court is expected to decide the case by June.

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