The US Supreme Court heard oral arguments Tuesday in California v. Texas, a case that could determine the future of the Affordable Care Act (ACA). This is the second time that the constitutionality of the ACA has been before the court, with the justices again being asked to review the individual mandate to buy health insurance as well as to decide whether the Act could stand if the individual mandate were struck down and whether the challengers even have standing to bring the case.

The court rejected a challenge on the constitutionality of the mandate in 2012 in National Federation of Independent Business v. Sebelius, justifying the mandate under Congress’ taxing power. But in a 2017 amendment to the ACA, Congress set the individual mandate penalty to $0, leading several states (including Texas) and two individuals to bring suit, arguing that the mandate is no longer a tax penalty, hence no longer constitutional. They also argued that the mandate was not severable, meaning that the entirety of the Act must fall were the mandate struck down. The Trump administration refused to defend the ACA in court, so California and several other states intervened, joined later by the House of Representatives, in defending the case. Last year, the US Court of Appeals for the Fifth Circuit on upheld a lower court decision invalidating the individual mandate, but did not decide the severability question.

Standing was a central issue in Tuesday’s oral argument. The individuals in the case claim that the mandate, despite its lack of penalty, has costs to them. Chief Justice John Roberts and Justice Clarence Thomas asked several questions probing this point, exploring whether a mandate can have consequences besides a penalty, such as opprobrium from others or a threat of enforcement. The states claimed that their burden has been increased by paperwork from increased healthcare enrollment and Internal Revenue Service reporting. The states also claimed standing because of burdens from other provisions of the ACA, but the three liberal justices and Roberts appeared hostile to this idea, which would expand standing doctrine.

Should the court reach the question of constitutionality, several justices seem ready to invalidate the mandate: since Sebelius eliminated other possible justifications for Congress’ creation of the mandate before holding that it could be construed as a tax, if it does not function as a tax then no other power permits it.

However, it appeared hard for the respondents to convince five justices that the whole of the ACA should fall if the mandate is unconstitutional. The statute’s challengers argued that Congress intended the ACA to work as a cohesive whole and did not design the mandate to be severable. Opposing counsel and skeptical justices argued that the law has been in place for three years basically without the mandate and that, moreover, the court typically severs when possible in complex legislative schemes that accomplish many purposes. As Justice Brett Kavanaugh said, “Looking at our severability precedents, it does seem fairly clear that the proper remedy would be to sever the mandate provision and leave the rest of the Act in place, the provisions regarding preexisting conditions and the rest.”