One question bound to come up during Tuesday's oral arguments in the legal challenge to Obamacare is whether the U.S. House of Representatives and 16 states can defend the law's constitutionality when the federal government will not.

The parties' arguments about standing have been streaming into the case because the U.S. Court of Appeals for the Fifth Circuit late last month ordered supplemental briefing and asked lawyers to address at oral argument how new case law impacts the interventions by the House and intervenor states. The Fifth Circuit also asked whether there's still a live case or controversy to decide on appeal.

In letter briefs filed last week, all of the parties agree that there's still a case or controversy in the appeal since the federal government has continued enforcing Obamacare as it appealed a district court's December 2018 ruling that the entire law is unconstitutional.

The appeal flipped in March when the U.S. Department of Justice told the Fifth Circuit that it agreed that the act is unconstitutional. Yet the 16 intervenor states and Washington, D.C., which intervened in the lawsuit very early at the district court level, are still defending Obamacare's constitutionality on appeal. More recently, the House intervened to defend the law.

Although they agree there's still a dispute for the Fifth Circuit to resolve, the parties disagree about the intervenors' standing.

The U.S. Department of Justice argued in a July 3 letter brief the House lacks standing because lawmakers haven't claimed any personal injury — rather, they have an institutional interest and want to defend their legislation, the letter said.

The government also argued that the state intervenors haven't met their burden to prove standing because they haven't shown how the district court's ruling injures them. This is because the ruling only applies in the states that attacked Obamacare as plaintiffs in the case, and not in the intervenor states, said the letter.

While the plaintiff states, led by Texas, agreed that the House lacks standing, they seemed puzzled by the federal government's argument that the district court only invalidated Obamacare in their state, not others.

The plaintiff states' July 5 letter by Texas Solicitor General Kyle Hawkins said if the district court ruling stands, it won't have geographic limits but will be unconstitutional nationwide. Hawkins wrote that the states that intervened would face an injury as they've alleged they'll lose federal funding if Obamacare is invalidated.

The House also argued that an unconstitutional Obamacare ruling would apply across the United States. However, it disputes the government and plaintiff states' claim that it lacks standing. A July 5 letter brief by Donald Verrilli Jr. of Munger, Tolles & Olson in Washington, D.C.,  argued that case law gives the House the right to intervene and defend a law when the Department of Justice refuses to do so.

“That is precisely what the House is doing — defending the law in its capacity as a representative of the federal government,” Verrilli wrote.

The intervenor states, lead by California, argued that they have standing because they face direct financial harm if Obamacare is held unconstitutional.

“Eliminating the act's Medicaid expansion provisions alone would cost the original 16 intervening state defendants and the District of Columbia more than $418 billion over the next decade,” said the state intervenors' July 5 letter by Samuel P. Siegel of the California Department of Justice.

Mootness?

Given the federal government's position on appeal, the Fifth Circuit also asked what should happen if the appeal is moot and none of the parties have standing to appeal.

Although all of the parties have urged the Fifth Circuit to move forward with the appeal, they disagree about what should happen if the court finds the appeal is moot.

The government and plaintiff states argued that the court should dismiss the appeal without vacating the district court's ruling.

On the other side, the House and intervenor states urged the court to vacate the district court's ruling. The House argued that vacating the ruling would serve the public interest because otherwise, a ruling that invalidated “one of the most significant statutes in U.S. history” would never have a chance for appellate review.