A federal judge yesterday allowed Eliot Spitzer to pursue, at least for the time being, an investigation into possible discrimination against minorities in mortgage lending that industry groups contend represents an attempt by the New York State attorney general to overstep the bounds of his authority.

U.S. District Court Judge Sidney Stein declined to issue a temporary restraining order to block Mr. Spitzer from requesting information from JPMorgan Chase, Wells Fargo, Citigroup, and HSBC. The Clearing House Association, a trade group, argued on behalf of the national banks that Mr. Spitzer does not have jurisdiction to conduct the investigation because they operate under charters granted by the federal government.

The judge did not hear arguments on a separate lawsuit filed last week by the U.S. Office of the Comptroller of the Currency, which is seeking to prohibit state inquiries into federally chartered financial institutions. The comptroller argues that the 1864 National Bank Act gives the federal government sole authority to regulate national banks, and that allowing Mr. Spitzer to continue this, or any other, investigation would hamper the federal regulator’s ability to oversee such institutions.

Judge Stein ruled yesterday that there was no compelling reason to stop Mr. Spitzer’s investigation until the issues are adjudicated. It is not clear when he will issue a final ruling in either lawsuit, both of which raise important questions about the scope of Mr. Spitzer’s regulatory authority.

Mr. Spitzer has frequently launched investigations of industries and companies that are regulated by federal agencies as well as states. But according to Michael Greve, director of the federalism project at the American Enterprise Institute, the case in question is one of the few in which Mr. Spitzer has ventured into territory that is the sole preserve of the federal government.

In his investigations of hedge funds, insurers, and mutual funds, Mr. Spitzer has justified state intervention by arguing that federal regulators were not exercising sufficient oversight, relying on New York State’s Martin Act. Some observers, however, believe that Mr. Spitzer has been stretching his authority.

“You can’t argue that the federal regulators aren’t interested” in investigating charges of discrimination, Mr. Greve said. Federal law is ironclad in granting the comptroller jurisdiction, he said, and federal regulators are paying attention to this issue, he said.

“Mr. Spitzer is not gap-filling,” Mr. Greve said. “He’s saying, ‘I’m better.’ “

A dean emeritus of the George Mason University School of Law, Henry Manne, said he doesn’t think Mr. Spitzer has any particular strategy to expand his office’s reach in federal territory. Rather, Mr. Manne said that Mr. Spitzer may just be courting public favor. “I think it’s a popular issue,” Mr. Manne said of the lending discrimination investigation. “Nobody likes creditors,” he said, which makes banks a good target politically.

Observers also agree that the case is noteworthy in that a federal regulatory agency is asserting itself in the face of Mr. Spitzer’s effort to encroach on its authority. The acting comptroller of the currency, Julie Williams, “is the first federal official who’s stood up to him,” said Alan Reynolds, a senior fellow at the Cato Institute.

Legal precedent appears to favor efforts to limit Mr. Spitzer in this instance, observers said. The Bank Act at the core of this case has been the subject of “endless struggle,” Mr. Greve said, so there is a large body of case law, and courts have generally ruled in favor of the federal government on regulating national banks.

The case comes after a two-decade long expansion of the power of state attorneys general that has occurred as the federal government has reduced regulation of many industries, Mr. Greve said. Mr. Spitzer, however, has been especially aggressive in pursuing what he claims are corporate wrongdoers.