With health insurance availability, cost and coverage on the line for millions of Americans, a federal appeals court seemed inclined to rule the core provision of President Barack Obama’s signature health care law is unconstitutional.

Two Republican-appointed judges on a three-judge panel of the U.S. Court of Appeals for the Fifth Circuit peppered lawyers defending the law with skeptical questions Tuesday, appearing to suggest they might hold that when Congress zeroed out a tax imposed by the law in 2017 it rendered unconstitutional the mandate to purchase health insurance.