Covington & Burling partner Robert Long said the invitation he received from the U.S. Supreme Court to participate in a challenge to the Patient Protection and Affordable Care Act was unexpected. But it didn’t take the veteran U.S. Supreme Court advocate long to accept.

“I didn’t really debate that issue very much,” said Long, whose pro bono participation as an amicus curiae in U.S. Department of Health and Human Services v. Florida marked his 17th argument before the Court.

In the four months leading up to the Court’s three-day hearing on the health care law in March, Long, chairman of his firm’s appellate and Supreme Court litigation group, spent hundreds of hours preparing to argue that the 1867 Anti-Injunction Act prohibited the 26 state attorneys general challenging the health care law’s individual mandate from bringing their suit. Under that position, which the U.S. Court of Appeals for the Fourth Circuit had taken and the Obama administration had abandoned, challenges to the landmark statute weren’t permissible until an individual is sanctioned for not buying health insurance as mandated by the law.

Although the Court ruled last month that challenges to the statute weren’t premature, Long garnered a compliment from the Court when he concluded his oral argument. “Mr. Long, you were invited by this Court to defend the proposition that the Anti-Injunction Act barred this litigation,” Chief Justice John Roberts Jr. said during the hearing. “You have ably carried out that responsibility, for which the Court is grateful.”

Long, a clerk from 1986 to 1987 to then-Justice Lewis Powell Jr. and an assistant to George H.W. Bush’s solicitor general, Kenneth Starr, said the kudos “felt good,” adding that his participation in the case wouldn’t have been possible without the encouragement of his firm.

“Covington & Burling could not have been more supportive,” he said.