Conservative policy adviser Avik Roy said in an interview that aired Tuesday on "Rising" that a U.S. District Court judge's move last week to strike down the Affordable Care Act (ACA) was a "classic case of judicial activism."

"I totally agree with some of the right-of-center writers, and obviously liberal writers, who have said this is a classic case of judicial activism, of the judge just saying 'I don't like ObamaCare so I'm just going to invent a reasoning to say that the whole law is unconstitutional,' " Roy, the president of the Foundation for Research on Equal Opportunity, told Hill.TV's Buck Sexton and Krystal Ball on Monday.

Roy served as a health-care policy adviser to Mitt Romney's 2012 presidential campaign and a senior adviser to Rick Perry's 2016 presidential campaign.

His comments come after Texas federal Judge Reed O'Connor struck down former President Obama's signature health-care law on Friday, arguing that the individual mandate cannot be separated from the rest of the law.

Roy disagreed with O'Connor's argument, saying the individual mandate is not needed for ACA to function.

"This whole conception that ObamaCare requires an individual mandate for the rest of ObamaCare to work, that's something that for eight years I've been disagreeing with, and I think the evidence has shown that that's true. Congress in 2017 zeroed out the penalty for the individual mandate and that year, the year after that, enrollment actually went up in the Affordable Care Act's exchanges," Roy said.

"So the individual mandate in ObamaCare, the specific one that was in there, wasn't as strong as a lot of people thought. It wasn't having the effect that a lot of people thought, and it's not necessary for the rest of ObamaCare to work," he added.

— Julia Manchester