Once every four to eight years, an incoming president has the opportunity to alter his predecessor’s legal positions in cases pending before the federal courts that have not been decided. Although these legal 180s are not uncommon, they could affect major decisions on the horizon.

Justice Elena Kagan, reflecting on her time as former President Barack Obama’s solicitor general, described such reversals as “a really big deal that people should hesitate a long time over.” Yet the Biden administration’s DOJ was quick to reverse several of the former Trump administration’s legal positions in early 2021, and the previous Trump presidency did the same for many of Obama’s legal positions.

Trump’s own appellate lawyer, who handled his criminal cases during the campaign, D. John Sauer, is preparing to take on the new role of solicitor general and will likely follow a similar pattern of reversing legal stances held by the Biden administration.

Last month, Thomas Wolf at the Brennan Center for Justice predicted that the next Trump administration could reverse the government’s position in at least half a dozen cases, in line with the Biden administration’s track record of legal U-turns. While such changes would be unsurprising, their impact could reshape significant areas of law, including cases pending before the high court and ones that could be granted for review in the near future.

At the same time, these changes do not automatically mean the justices would shift their opinions. In the five legal positions Biden’s administration reversed from his predecessor when he took office, his position lost in four cases, according to Wolf.

Here are the top cases currently before the Supreme Court, or ones that could soon land before the justices again, that the Trump administration could reverse Biden’s positions on:

Laws barring transgender procedures for minors

Case: United States v. Skrmetti

Issue: Whether Tennessee’s ban on gender-affirming care for minors violates the equal protection clause.

The Biden administration has argued that Tennessee’s law discriminates against transgender youth and violates constitutional protections.

The Supreme Court heard oral arguments in the case on Dec. 4, 2024, just weeks before the Trump DOJ is expected to reverse the government’s position, aligning with Tennessee and arguing the law is a valid exercise of state authority.

Some legal experts question how the Supreme Court will proceed if the Trump administration reverses the Biden administration’s stance and supports Tennessee’s law.

Ed Whelan, citing Justice Sandra Day O’Connor’s 1983 opinion in Director, OWCP v. Perini North River Associates, has suggested the Supreme Court can still decide the case as long as a valid controversy exists, even if the federal government changes its position. In this case, the Biden administration swept in to defend ACLU plaintiffs challenging the law, and those parties will remain opposed to Tennessee’s law regardless of the departing Biden administration.

If the eventual majority opinion upholds the law, similar measures in other states are expected to be bolstered by the decision and could set a broader trend for states deciding whether to permit transgender procedures for minors.

Will Trump throw ‘ghost guns’ enthusiasts a favor?

Case: Garland v. VanDerStok

Issue: Whether firearm parts kits qualify as “firearms” under federal law.

The Supreme Court is reviewing a Biden-era Bureau of Alcohol, Tobacco, and Firearms rule regulating untraceable firearm kits, known as ghost guns. But judging by the tone of oral arguments in early August 2024, a majority of the justices seemed inclined to uphold the rule.

Regardless of the Supreme Court’s decision, Trump will likely have to weigh competing interests between gun control advocates and gun rights groups pressing him to repeal the rule, and he will likely face pressure to file an amended brief at the Supreme Court in opposition.

The NRA and Gun Owners of America have cited Trump’s promises to roll back Biden-era regulations on firearms.

Additionally, Trump took heat from pro-gun advocates over a decision in his first term to throw his support under an ATF “bump stocks ban” following the 2017 Las Vegas mass shooting. The Supreme Court held in 2024 that the ban was unconstitutional in Cargill v. Garland.

The pro-gun control Brady Center warns that reversing these rules would undermine efforts to address the rising problem of ghost guns in criminal activity, such as the suspected UnitedHealthcare CEO killer, who was arrested near a Pennsylvania McDonald’s carrying the untraceable-style handgun.

Flavored vape products and overregulation

Case: Food and Drug Administration v. Wages and White Lion Investments, LLC

Issue: Whether the FDA’s denial of marketing applications for flavored e-cigarettes was arbitrary under federal law.

Vape manufacturer Wages and White Lion Investments accuse the FDA of changing its application process for approving their flavored e-cigarette products. The company included its plan to prevent youths from accessing the products in a September 2020 application to the agency, only for the FDA to announce new application requirements 11 months later and subsequently deny pending applications for Wages and White Lion.

The case is not just about the vaping industry but has the chance to address what regulatory critics often cite as shifting goalposts by the FDA, according to Pacific Legal Foundation, which is representing the vape manufacturers.

During oral arguments, Justice Clarence Thomas noted that the vape manufacturers bringing the case alleging the FDA’s guidance was “actually a moving target.”

The Biden administration has defended its strict regulatory stance, citing youth nicotine addiction. During arguments, justices highlighted both the FDA’s reasoning and claims by manufacturers of unfair treatment.

The Trump administration could pivot to supporting the vape industry, such as rolling back restrictions and signaling a more permissive regulatory environment.

Blue-state emissions regulations could face setbacks

Case: Diamond Alternative Energy, LLC v. EPA

Issue: Whether fuel producers have standing to challenge California’s stricter vehicle emissions standards.

The lawsuit focuses on California’s EPA waiver, reinstated by the Biden administration in 2022, which allows the state to enforce tougher emissions rules. The Supreme Court, which only just granted the case last month, will hear arguments next year.

The justices are not expected to review the legality of the waiver itself but will decide if fuel producers have legal standing to challenge it.

The case highlights a sharp policy divide. The Trump administration previously rescinded California’s authority in 2019 and would likely renew efforts to revoke waivers, prioritizing uniform national standards and boosting fossil fuel production.

Under Attorney General Merrick Garland, Solicitor General Elizabeth Prelogar has said the petitioners lack standing to sue over the waiver because they have not demonstrated a direct injury resulting from the EPA’s decision. However, given Trump’s pro-industry stance, his new administration could argue that the fuel producers have been harmed.

A ruling for fuel producers could weaken California’s climate policies and encourage broader deregulation of state-led environmental initiatives.

Another abortion pill challenge looms

Case: Missouri, Kansas, Idaho v. U.S. Food and Drug Administration

Issue: A revised lawsuit filed by Missouri, Idaho, and Kansas challenges the FDA’s 2016 updates expanding access to mifepristone, one of two medications taken by women who undergo chemical abortions.

The Biden administration defended FDA approval of the abortion pill, but the new lawsuit targets telemedicine access, shield laws, and minors’ use of the drug. Judge Matthew Kacsmaryk, who previously ruled against the FDA’s approval, is overseeing the case.

The Supreme Court already decided a previous version of this case in 2024. Religious doctors who objected to the FDA’s mifepristone approval were denied relief due to the majority finding that they, as individuals, lacked the standing to challenge expanded access to the drug.

If the Supreme Court hears the case, a Trump administration could argue for stricter abortion medication regulations but would have to weigh competing interests from his anti-abortion supporters and moderates who have appreciated his hands-off position.

Trump has been inconsistent in his response to whether he would make efforts to curtail access to mifepristone. In August 2024, campaign spokeswoman Karoline Leavitt clarified that the then-candidate wanted to leave the issue of abortion drug access to something that is for “everybody to vote,” reiterating his position that it should be left to the states to decide.

But in recent days, Trump has saddled back to the position that he does not intend to restrict mifepristone.

Due to Trump’s hands-off approach, it might be up to the conservative states that filed suit to prove in court that the FDA erred when it expanded access to the chemical abortion drug by males in the mid-2010s.

Will DACA once again be in Trump’s crosshairs?

Case: State of Texas v. United States

Issue: Whether Deferred Action for Childhood Arrivals policy, protecting undocumented individuals brought to the U.S. as children, is lawful.

The U.S. Court of Appeals for the 5th Circuit heard arguments in October 2024 over Texas’s bid to rule against the program, after U.S. District Judge Andrew Hanen declared it illegal in September 2023. Legal experts say the more conservative-leaning appellate court looks poised to uphold Hanen’s decision, according to analysis from the recent arguments, and a decision could come within weeks.

While the district court ruling does not impact DACA recipients under the protections of the law, the ongoing legal fight has shown an elevated scrutiny of DACA by the courts compared to just a few years ago.

After the first Trump administration sought to end DACA, it eventually appealed to the Supreme Court in light of several lawsuits geared at keeping the law in place. In a narrow 5-4 decision in 2020, the Supreme Court affirmed lower court positions that the Trump administration filed to follow proper procedure when attempting to rescind DACA.

Because of these previous unsuccessful efforts to repeal DACA, the new Trump administration could foreseeably try to reverse the current administration’s defense of DACA, potentially impacting more than 500,000 beneficiaries.

On the other hand, Trump said last month he wants to support a legislative solution to keep “Dreamers,” people who came to the U.S. illegally as children and have lived in the country for many years.

“I will work with the Democrats on a plan,” Trump said.

Although Trump’s DOJ could file an amended brief to the 5th Circuit that might reverse the Biden administration’s pro-DACA stance, the incoming administration could just as easily allow the case to proceed with no additional filings, await the appellate court’s decision, and develop an official stance if a Supreme Court appeal is imminent.