CNN– The Supreme Court on Tuesday heard oral arguments in two challenges to President Joe Biden’s student debt relief plan, with several conservative justices appearing skeptical of the government’s authority to discharge millions of dollars in federally held loans.

If the conservatives do ultimately rule in favor of the policy’s challengers, the hearing made clear they will have to grapple with the legal questions around why states and individual borrowers should be allowed to sue over the program – questions that emerged as a flash point during the arguments.

Millions of qualifying student loan borrowers could see up to $20,000 of their debt canceled depending on the outcome of the arguments. How and when the justices rule will also determine when payments on federal student loans will resume after a pandemic-related pause was put in place nearly three years ago.

In Biden v. Nebraska, a group of Republican-led states argued the administration exceeded its authority by using the pandemic as a pretext to mask the true goal of fulfilling a campaign promise to erase student loan debt.

The second case is Department of Education v. Brown, which was initially brought by two individuals who did not qualify for the full benefits of the forgiveness program and argue the government failed to follow the proper rulemaking process when putting it in place.

Here are takeaways from the oral arguments:

Conservatives see this case as another chance to rein in aggressive actions by Biden

In the questions the conservative justices posed, they signaled that they see the GOP states’ case as presenting the court with another chance to draw the lines around when the executive branch can and cannot act without Congress.

Several of the exchanges concerned the application of the so-called “Major Questions Doctrine,” a legal theory embraced by the court’s Republican appointees that says Congress can be expected to speak with specificity when it gives an agency power to do something of great political or economic significance.

The states are arguing that under the doctrine, the Biden student debt program should be blocked.

Chief Justice John Roberts raised the doctrine as he told US Solicitor General Elizabeth Prelogar that the case “presents extraordinarily serious important issues about the role of Congress.”

“We take very seriously the idea of separation of powers and that power should be divided to prevent its abuse,” Roberts said.

Justice Brett Kavanaugh asked Prelogar to compare the dispute with cases in the court’s history where the court ultimately pushed back against government claims that a national emergency justified the aggressive, unilateral action by the executive branch.

Conservatives bring up Covid-19 authority and knowledge

Kavanaugh also sought some context on how the court should see the current dispute over student debt relief fitting within the larger spectrum of other cases dealing with executive branch actions aimed at the Covid-19 pandemic.

In some of those Covid-19 cases, Kavanaugh noted, the court ruled that the agency exceeded its authority, and in others, the action was upheld – particularly when an executive branch action was found to be in the “wheelhouse” of the agency that implemented it.

Justice Neil Gorsuch, meanwhile, asked Nebraska Solicitor General James Campbell, who is representing the red states, a series of questions that seemed aimed at helping the court further flesh out the doctrine.

“I understand the Secretary [of Education] has considerable expertise when it comes to educational affairs,” Gorsuch said. “But … in terms of macroeconomic policy, do we normally assume that every secretary Cabinet member – as learned as they are – has that kind of knowledge?”

The question suggested Gorsuch’s skepticism to the idea that Congress would have given the secretary of education the power – without more explicit language in the statutory – to do the sort of mass student debt cancellation that could affect the larger economy.

Lawyer for GOP states gets grilled on standing

Whether the GOP states are threatened by the type of harm that makes it appropriate for a court to intervene was a major theme. Campbell received a series of questions – from justices on both sides of the ideological spectrum – about whether the states had overcome this procedural threshold, which is known as “standing.”

A particular flashpoint in the hearing was the states’ arguments that the loan forgiveness program’s potential harms to MOHELA – the Missouri-created entity that services loans in the state – gives Missouri standing. Several justices noted that MOHELA could have filed its own lawsuit challenging the program, but has not.

“Usually, we don’t allow one person to step into another’s shoes and say, ‘I think that that person suffered harm,’ even if the harm is very great,” Justice Elena Kagan told Campbell. “So why isn’t MOHELA responsible for deciding whether to bring this suit?”

Later on, Kagan pointed out that the state of Missouri was so disconnected from MOHELA that the state had to file an open-records request to get the records from MOHELA that it needed from the lawsuit.

Justice Ketanji Brown Jackson also pressed Campbell on whether the supposed harms the loan forgiveness program would cause MOHELA had really established standing for Missouri.

Barrett may be a justice to watch – but her vote alone won’t be enough to save Biden’s program

Justice Amy Coney Barrett has stood out among the conservatives for asking particularly pointed questions of the GOP states about their standing arguments, setting her apart as a potential pickup vote for the court’s three liberal members.

“If MOHELA is an arm of the state, why didn’t you just strong-arm MOHELA and say you’ve got to pursue this suit,” Barrett asked Campbell, among several questions she asked him about the states’ standing claims.

In another sign of her skepticism toward the states’ standing arguments, she also asked whether the state of Missouri also filed a lawsuit to vindicate the interests of the city of St. Louis.

Even if Barrett swings to the liberals to vote that the lawsuit should be rejected because of the standing concerns, the Biden administration will need the vote of one more GOP-appointed justice.

Sotomayor raises the practical stakes of the case

In extended remarks to Campbell, Justice Sonia Sotomayor laid out the practical implications of the case in stark terms.

“There’s 50 million students who are – who will benefit from this. Who today will struggle. Many of them don’t have assets sufficient to bail them out after the pandemic. They don’t have friends or families or others who can help them make these payments,” she remarked. Those debtors will suffer in ways others won’t because of the pandemic, she said.

“And what you’re saying is now we’re going to give judges the right to decide how much aid to give them instead of the person with the expertise and the experience, the secretary of education who’s been dealing with educational issues and the problems surrounding student loans,” she said.

Conservatives ask if Biden’s plan is fair since not everyone benefits

Some of the court’s conservative members leaned into the individual plaintiffs’ – two borrowers – claims they were unlawfully deprived of a notice-and-comment period to argue to the agency that the program wasn’t fair to them.

Those justices peppered Prelogar with questions about whether Biden’s proposed student loan forgiveness program is fair in respect to people who won’t benefit – those who have already paid off their student debt or never took out student loans to begin with, for example.

After justices, including Roberts, asked several times about the fairness of the program, Justice Samuel Alito posed the question again.

“Why was it fair to the people who didn’t get arguably comparable relief, not maybe that their interests were outweighed by the interests of those who were benefited or they were somehow less deserving of solicitude,” Alito asked.

“My answer to that question is that Congress has already made the judgment that when there is a national emergency that affects borrowers in this way, the secretary can provide relief,” Prelogar replied.

That line of questioning also received pushback from some of the court’s liberal members, including Sotomayor, who said at one point that there is an “inherent unfairness in society because we’re not a society of unlimited resources.”

“I think the bottom-line answer to be, everybody suffered in the pandemic. But different people got different benefits because they qualified under different programs, correct?” Sotomayor said.

Jackson echoed that point, telling Prelogar, “I’m wondering whether or not the same fairness issue would arise with respect to any federal benefit programs.”

This story has been updated with additional details.

CNN’s Katie Lobosco contributed to this report.