Consumer groups cheered a Supreme Court decision in 2015 that upheld the use of a legal theory called disparate impact under the Fair Housing Act, though the court included some limits on its application. The theory says that business standards or practices can in some cases be considered discriminatory if certain groups are negatively impacted, even if unintentionally.

But with the change in administration and a focus on deregulation, the banking industry is looking for a swing back. The Justice Department “will be a lot more selective in the cases that they pursue, and it’s unlikely they will get involved in cases unless there’s out-and-out evidence of discrimination,” said Alan Kaplinsky, a partner specializing in consumer financial regulation at Ballard Spahr.

A spokesman for the Justice Department declined to comment on the agency’s enforcement plans.

Stuart Rossman, director of litigation at the National Consumer Law Center, said that consumer advocates had been discussing the implications for enforcement of the country’s fair lending laws since the November elections, when Republicans won the White House and secured both chambers of Congress.

“We are watching with great interest and concern,” he said.

Lisa Rice, executive vice president at the National Fair Housing Alliance, said that she had “measured hope” for the incoming administration. Attorney General Jeff Sessions “did say that he was going to vigorously enforce the law,” Ms. Rice said. “We will be holding his feet to the fire and we will be pushing and making sure that he lives up to the promise that he made during his confirmation process and that he fully enforces all of the components of the Fair Housing Act.”

For now, the Consumer Financial Protection Bureau remains a bright spot for advocates. The agency has pursued a host of fair lending cases under the Equal Credit Opportunity Act since its founding in 2011, often in conjunction with the Justice Department. The bureau signaled in December that it would focus on redlining, unfair treatment in mortgage and student loan servicing and discrimination in small business lending this year. It said in April that it obtained $108 million from financial institutions for fair lending violations in 2015.

“In the coming years we will continue to build on our record of steady and vigorous enforcement of the fair lending laws,” Patrice Ficklin, head of the consumer agency’s fair lending office, said in a statement. “Discrimination in mortgage lending continues to be a key priority, and we have focused in particular on redlining risk.”

Still, the fate of the consumer agency under the Trump administration is unknown. It is not clear whether its director, Richard Cordray, will be allowed to serve out the rest of his term, which expires next year, or whether lawmakers in Congress will succeed in replacing the single director with a commission or in limiting the agency’s enforcement powers. If the bureau were to take a back seat on fair lending, observers predicted that individual states could move in to help fill the void.