The Supreme Court’s three-year embrace of the McCain-Feingold campaign finance reform law seemed to loosen Wednesday, as justices debated a First Amendment challenge to the law’s provision that bars certain types of issue advertisements in the run-up to elections.

A majority of justices questioned one or another aspect of the provision during hourlong arguments in Federal Election Commission v. Wisconsin Right to Life. The case is an “as-applied” challenge to the ban on “electioneering communications” directly funded by corporations and unions 30 days before primary and 60 days before general elections. The Court, with now-retired Justice Sandra Day O’Connor in the majority, upheld the law on its face more than three years ago in McConnell v. FEC, but the justices left the door open to challenges once the law took effect.