And Roberts also spoke about the uniqueness of health care, which almost everyone uses at some point.
"Everybody is in this market, so that makes it very different than the market for cars or the other hypotheticals that you came up with, and all they're regulating is how you pay for it," Roberts said, paraphrasing the government's argument.
Kennedy and Roberts emerged as the apparent pivotal votes in the court's decision.
Associated Press writers Jesse J. Holland and Jessica Gresko contributed to this report.
Also of interest: Health Care Law fact sheets.