WASHINGTON — In 2012, the Supreme Court declared that Congress had put “a gun to the head” of states by pressuring them to expand Medicaid, and it said that such “economic dragooning” of the states violated federalism principles embedded in the Constitution.

Now, in a separate case, comments by several justices indicate that they could uphold a pillar of the Affordable Care Act — insurance subsidies for millions of lower-income people — by invoking those same principles.

In 2012, the court said it would be unconstitutional for Congress to cut off all Medicaid payments to states that refused to expand eligibility, and this ruling instantly transformed the expansion of Medicaid into a state option.

That precedent echoed through oral arguments last week before the court; justices again expressed respect for federalism and state sovereignty.