The Supreme Court appeared unlikely Tuesday to second-guess how Congress denies residents of Puerto Rico certain Social Security benefits — particularly when a clause in the Constitution gives lawmakers broad power over territories.

A resident of Puerto Rico challenged a 1972 law as unconstitutional because it provides Supplemental Security Income for aged, blind and disabled individuals, but not in Puerto Rico and most other U.S. territories. Lower courts ruled that different treatment under a national program violates the rights of U.S. citizens in Puerto Rico.

But several justices aired concerns during oral argument about how such an outcome could affect other laws that treat the territory differently from states, or could change the terms of the nation’s founding document.

The justices will issue a decision before the end of the term in late June. A decision that requires the United States to include Puerto Rico residents in the program could cost an additional $23 billion over the next decade.

An attorney defending the law for the United States said Congress has the power to draw distinctions about how residents in Puerto Rico are treated under federal laws, and a clause in Article IV means “the Constitution itself recognizes this as a legitimate dividing line.”

Deputy Solicitor General Curtis Gannon said Congress based its decision about SSI benefits on policy considerations, such as the fact that Puerto Rico residents don’t pay federal income tax. He said different treatment is based on location, not on ethnicity or race, as the challengers contend.

“They are U.S. citizens, but there is no evidence here linking this exclusion to ethnicity or discrimination,” Gannon said.

Justice Elena Kagan said that theory would seem to apply equally well to any benefits programs, and if that’s the case then “the lesson going forward is Congress can do this whenever it wants.”

Kagan later asked Hermann Ferré, the attorney arguing for Puerto Rico resident Jose Luis Vaello-Madero, why that clause doesn’t settle the case by itself since it “goes pretty far towards authorizing Congress to make rules about the territories,” which may inevitably mean it can “make distinctions between the territories and other parts of the United States.”

Ferré told the justices that congressional power over territories was intended to be temporary. But he said previous Supreme Court rulings created a situation that “could potentially be abused” if Congress steps in without actually guiding the territory toward statehood or independence.

“So the court essentially blessed the possibility of territories remaining territories in an indefinite state without full participation, without a full seat at the table,” Ferré said.

Chief Justice John G. Roberts Jr. and Justice Samuel A. Alito Jr. were among the justices who raised concerns about how a decision could affect other laws that treat Puerto Rico and other territories differently from the 50 states.

Roberts asked whether an argument not to exclude Puerto Rico in SSI benefits would also apply to every federal benefits program. And Alito asked what the difference was between this law and laws that favor residents of particular states, such as the deductibility of state and local taxes when filing federal income taxes.

Alito also asked whether a decision siding with the challengers would allow a resident of a state to claim their equal protection rights were violated “because he or she was required to pay federal income tax and residents of Puerto Rico are not.”

And Justice Brett M. Kavanaugh said Ferré had made some compelling policy arguments but that the clause at issue in this case is similar to other parts of the Constitution that some people may consider anachronistic.

It would take amendments to change some provisions — such as the number of senators per state or the Electoral College — and the clause in Article IV gives the authority over territories to Congress and not the court, Kavanaugh said.

The case centers on one man with severe health problems, Vaello-Madero, a U.S. citizen born in Puerto Rico who moved to New York and then, in 2013, back to Puerto Rico and thereby lost eligibility for the benefits.

Justice Sonia Sotomayor said during arguments that “needy is needy,” whether in the 50 states or Puerto Rico, and Congress needs to have a rational reason for the different treatment.

“I’m just not quite sure why one would say that it’s rational to treat a group of people, of citizens, differently from other citizens on the mainland when the need is the same,” Sotomayor said.