Biden's student-loan forgiveness plan is in jeopardy. Here are 4 major takeaways from the Supreme Court's oral arguments.

• The Supreme Court heard oral arguments for Biden's student-debt relief on Tuesday.
• Conservative justices appeared skeptical of the plan, suggesting it could be in trouble.

President Joe Biden's student-loan forgiveness could be in trouble as a majority of the Supreme Court's conservative justices questioned his authority to enact sweeping relief.

The nation's highest court heard more than four hours of oral arguments in two high-profile cases that reviewed Biden's plan to cancel up to $20,000 in debt for federal borrowers, which lower courts temporarily paused in November.

Tuesday's first case involved six Republican-led states – Arkansas, South Carolina, Iowa, Kansas, Nebraska, and Missouri – that argued the debt relief would hurt their states' revenues, along with the revenue of Missouri-based student-loan company, MOHELA.

The second case was brought by two student-loan borrowers, backed by the conservative Job Creators Network, who sued because they did not qualify for the full $20,000 amount of debt relief — one did not receive a Pell Grant so he could not get the full amount, and another had commercially-held loans that are not eligible under Biden's plan.

The Biden administration has argued that the states and the borrowers lack standing, or the power to block the plan by showing they suffered an injury from it, and that the HEROES Act of 2003 allows the education secretary to waive or modify student-loan balances amid a national emergency, like the COVID-19 pandemic.

"The argument throughout both of the sessions emphasized that the pandemic had really devastating financial effects on low and middle income student loan borrowers," Josh Rovenger, senior attorney in the Economic Justice Practice Group at The Legal Aid Society of Cleveland and fellow at advocacy group Student Borrower Protection Center, told reporters after the arguments concluded. "And that the risk of default upon returning to repayment without cancellation would be quite staggering."

The lengthy and spirited debate over Biden's debt relief largely fell along ideological lines as the court's conservatives repeatedly questioned whether Education Secretary Miguel Cardona exceeded his power, while the liberal justices said that he acted within his authority.

Rulings are expected in both of the cases by June. Should a majority of the court decide that Biden's plan is unconstitutional, then the implementation of the relief may be narrowed — or borrowers could get no help all.

Here are four major takeaways from Tuesday's oral arguments:

Conservatives worry about executive overreach

The language of the HEROES Act dominated oral arguments as the conservative justices scrutinized whether Biden's plan – a "cancellation" of debt – can be justified as a waiver or modification of student-loan balances.

"We're talking about half a trillion dollars and 43 million Americans," Chief Justice John Roberts said, referring to the estimated costs of Biden's plan and the number of affected borrowers. "How does that fit under the normal understanding of 'modifying'?"

The Biden administration, represented by US Solicitor General Elizabeth Prelogar, maintained that a cancellation or discharge of debt falls under the "waive and modify" language.

"It couldn't have surprised Congress one bit that in response to hardship posed by a national emergency, the secretary might consider similarly providing discharge if that's what it takes to make sure borrowers don't default," she told Roberts.

But most of the court's conservatives appeared skeptical, suggesting that Congress did not intend for the law to be used in this way and it could demonstrate executive overreach.

"Given the posture of the case, and given our historic concern about separation of powers," Roberts said, "You would recognize at least that this is a case that presents extraordinarily serious, important issues about the role of Congress and about the role that we should exercise in scrutinizing that?"

Justice Clarence Thomas also questioned how the sweeping relief could be considered a "modification."

"I think that forbearance fits more comfortably in 'waive or modify' language, it's you simply forbearing on collecting an underlying debt, but you don't cancel a debt, and that's what we're talking about here," he said.

The court's liberals, on the other hand, appeared to embrace the Biden administration's stance, saying that Congress clearly addressed the education secretary's authority in the law.

Justice Elena Kagan raised a hypothetical national emergency of an earthquake and the education secretary responded by deciding to cancel student loans for those harmed.

Didn't Congress give the secretary power to say, "Oh my gosh, people have had their homes wiped out, we're going to discharge their student loans?" Kagan asked Nebraska Solicitor General James Campbell, who represented the states challenging the relief.

Neil Gorsuch questions fairness of relief, Education Secretary's economic "expertise"

A common GOP argument against student-debt relief is that it's unfair to Americans who wouldn't benefit — and Justice Neil Gorsuch appeared to raise that concern. He questioned what the "cost" of the plan is "in terms of fairness" to people who have paid their loans, who haven't taken out loans, or who are ineligible for loans in the first place.

Roberts also said that "I think it appropriate to consider some of the fairness arguments."

Gorsuch also threw into question how big of an influence the Education Department should have on major economic decisions.

"I understand the [Education] Secretary has considerable expertise when it comes to educational affairs, but in terms of macroeconomic policy, do we normally assume that every cabinet secretary – learned as they are – has that kind of knowledge?" Gorsuch asked.

Liberal justices scrutinize standing, emphasize financial impacts of pandemic

Proving standing in a lawsuit means showing that the plaintiff would be injured by the policy, that the injury can be directly traced back to the defendant, and that the relief they're seeking would address those injuries.

The three liberal justices – Kagan, Sonia Sotomayor and Ketanji Brown Jackson – drilled into the questions of standing in both of the cases, in particular the involvement of the student-loan servicer MOHELA in the case brought by the states. MOHELA previously said it's not involved in the case, and the Biden administration argued MOHELA can sue and be sued on its own, and should not be used in the states' defense.

"If MOHELA is being injured as a result of the plan, or at least if that's the allegation, MOHELA has the ability to defend itself and its interests, correct?" Jackson asked Prelogar in the states' case.

"I feel like we really do have to be concerned about jumping into the political fray unless we are prompted to do so by a lawsuit that is brought by someone who has an actual interest," Jackson said at another point. "So this is why I'm sort of pressing really hard on the standing point."

Abby Shafroth, director of the Student Loan Borrower Assistance Project at the National Consumer Law Center, told reporters after the arguments concluded that standing is "a gatekeeper of the court."

"The courts cannot do anything to interfere with executive power or congressional power if they do not have authority under the Constitution to act," Shafroth said. "Standing is one of the things that is a requirement for them to have that authority."

"They can't resolve the case or strike down cancellation in these cases if the parties in these cases do not have standing," Shafroth added.

Aside from the standing issue, the liberal justices also weighed in on the substantive questions about the forgiveness plan. Biden's administration has repeatedly emphasized that the financial impacts of the pandemic could extend long after a national emergency declaration ends, and Justice Sonia Sotomayor raised that point.

"There's 50 million students who will benefit from this who today will struggle. Many of them don't have assets sufficient to bail them out after the pandemic," Sotomayor said. "They don't have friends or families or others who can help them make these payments. The evidence is clear that many of them will have to default. Their financial situation will be even worse."

"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," she added.

Amy Coney Barrett might join liberal justices on standing

Justice Amy Coney Barrett, a conservative, could be one justice to watch when it comes to whether Biden's plan stands. Similar to the court's liberals, she also led a tough line of questioning with Nebraska's solicitor general on standing and MOHELA's role in the case.

"Do you want to address why MOHELA is not here?" Barrett asked. "Why didn't the state just make MOHELA come then?"

"If MOHELA is an arm of the state, why didn't you just strong arm MOHELA and say, 'You've gotta pursue this suit'?" Barrett continued.

Campbell responded that Missouri has an interest in MOHELA and the "authority to assert its interests."

Still, even if Barrett and the court's three liberals find that the states and borrowers lack standing, they would need another conservative vote to uphold Biden's debt relief.

After the arguments, White House spokeswoman Olivia Dalton told reporters traveling with Biden that the administration is confident its plan will prevail.

"The bottom line is we're confident in our legal authority which is why we've taken this case all the way to the Supreme Court on behalf of 40 million Americans who need a little bit more breathing room," she said.