Justices Amy Coney Barrett and Ketanji Brown Jackson forcefully butted heads in dueling opinions Friday regarding President Trump’s executive order narrowing birthright citizenship.

The Supreme Court’s majority opinion, penned by Barrett and joined by the high court’s other five conservative justices, lets Trump’s order go into effect for now in some parts of the country, by curtailing judges’ ability to issue universal injunctions.

Jackson joined her fellow liberal justices in a fiery, joint dissent, but further claimed in a solo dissent that the court’s decision marked an “existential threat to the rule of law.”

The Trump administration’s bid to “vanquish” universal injunctions amounts to a request for the high court’s permission to “engage in unlawful behavior,” Jackson said, implying that the majority gave Trump just that.

“It gives the Executive the go-ahead to sometimes wield the kind of unchecked, arbitrary power the Founders crafted our Constitution to eradicate,” she wrote.

Barrett sharply rebuked Jackson’s rhetoric as a “startling line of attack” and said she would not dwell on her “extreme” argument, claiming it is at odds with centuries of precedent and the Constitution itself.

“We observe only this: Justice Jackson decries an imperial Executive while embracing an imperial Judiciary,” Barrett wrote. “No one disputes that the Executive has a duty to follow the law. But the Judiciary does not have unbridled authority to enforce this obligation—in fact, sometimes the law prohibits the Judiciary from doing so.”

She continued to suggest that Jackson should “heed her own admonition.”

“‘[E]veryone, from the President on down, is bound by law,’” Barrett wrote, quoting Jackson. “That goes for judges too.”

The high court’s decision revokes a key tool plaintiffs have used to beat back Trump’s agenda in dozens of lawsuits, finding that three federal district judges overstepped in issuing universal injunctions against Trump’s birthright citizenship order, which restricts such citizenship for children born on U.S. soil if at least one parent does not have permanent legal status.

The justices left for another day the question of whether the restrictions are constitutional.