A new legal challenge could upend a law President Trump has consistently highlighted as one of his signature legislative achievements, which marks the most significant shift to civil service statutes in decades.

Jeffrey Sayers, a former Veterans Affairs Department pharmacist for 37 years and until recently the chief of pharmacy in the Los Angeles area, brought his case to the U.S. Court of Appeals for the Federal Circuit after an executive branch judge upheld VA’s decision to fire him. In his appeal, Sayers argued the firing was “arbitrary and capricious.” He went further, however, saying the provisions of the 2017 VA Accountability and Whistleblower Protection Act used to expedite his removal violated his due process rights, failed to use the proper burden of proof and improperly circumvented the merit system principles afforded to all civil servants.

The case has potential for a far-reaching impact, as the federal circuit court could issue a precedent-setting ruling on the constitutionality of the 2017 law. A previous effort to ease the firing of just Senior Executive Service employees at VA signed into law by President Obama was eventually struck down in federal court, and the department stopped using the authority.

So far, Sayers’ case was heard only by an administrative judge at the Merit Systems Protection Board. That board’s central panel is without a quorum and therefore cannot rule on cases appealed to it, so Sayers opted to skip that step and go directly to federal court. The court could decide to take a more narrow approach, as Sayers also argued his alleged performance issues occurred before the law went into effect and VA improperly applied its provisions retroactively. If the court remands his case on that basis alone, the larger underlying questions would remain unanswered.

James Solomon, an attorney for Sayers, said he wrote the appeal with the direct intention of forcing the court to issue a broad ruling on the law. Without guidance from the central board, he said, MSPB judges are interpreting it differently, leading to disparate outcomes.

Administrative Judge Samantha Black, for example, said she could only determine the veracity of the facts of the case, but not weigh in on the appropriateness of the penalty applied. According to Solomon, that amounted to a violation of the “Douglas factors” that under court precedent must apply to all federal employee discipline.

“The Board does not have the authority to mitigate the penalty prescribed by the agency,” Black wrote in her decision. “I understand a limitation on the Board’s ability to mitigate a penalty as a limitation on the Board’s authority to assess the factors considered or the weight accorded any particular factor in selecting a penalty.”

Even if Sayers had done what VA has accused him of, Solomon said, it improperly applied its own table of penalties. The attorney said allegations such as improperly maintaining expired prescription drugs should have led only to a reprimand, not a firing. VA also violated merit system principles by not providing Sayers with a performance improvement plan and an opportunity to correct his alleged behavior, Solomon said.

The 2017 law allows VA to remove any employee on an expedited time frame using a reduced burden of proof. Federal agencies typically have to demonstrate a “preponderance of evidence,” meaning it is more likely than not that the employee is guilty, but the law allowed VA to instead demonstrate only “substantial evidence.” Sayers argued VA improperly applied that lower threshold in his case, as the law meant for it to be applied only upon appeal.

Additionally, the former pharmacist and his legal team said the expedited timeline to respond to the department’s notice of termination and appeal was insufficient to craft a fair defense and therefore violates the due process clause of the Constitution.

Solomon said the lowering of the evidence threshold has led to “lazy decision-making." Because of the reduced burden of evidence, Natalie Khawam, the lead member of Sayers’ legal team at The Whistleblower Law Firm, wrote in her brief, “Nobody applied true discretion and/or objective reasonableness at any point before or after removing Dr. Sayers.”

Khawam is also seeking to use Trump’s own words against him, highlighting the president’s remarks when boasting about the measure earlier this year.

“Employees ‘could steal money, and you couldn’t do anything about it,' ” the attorney quoted Trump as saying. “‘Now you can do whatever you want.’” Khawam added that Trump “is correct; unless this Circuit Court of Appeals forces the agency to rein in their application of the act, a deciding official can do virtually whatever they want.”

Highlighting the potential gravity of Sayers’ case, the American Federation of Government Employees weighed in with a supportive amicus brief filing, a rare instance of the union speaking up for a management employee not eligible for its representation. AFGE focused its argument on MSPB’s refusal to weigh in on “the reasonableness of the penalty,” saying without such consideration the judge’s decision must be reversed.

Solomon said if the Federal Circuit issues a narrow decision, he has other, similar cases that he will appeal using the same argument until it rules on the larger validity of the law. In one case, in which the Office of Special Counsel has since intervened, Solomon said VA proposed to fire an employee for an alleged three-year old Privacy Act violation only after she reported $10 million in missing equipment and accused her supervisor of sexual harassment.

“This is something they’re going to have to decide on so the hope is they just do it all now,” Solomon said.

Curt Cashour, a VA spokesman, said he could not weigh in on the details of the law without written consent from Sayers, which Sayers did not provide. He noted, however, that the accountability act cleared Congress with ease and had support from nearly all veterans service organizations.

“There is widespread, bipartisan agreement that it has been too difficult to remove or suspend VA employees who don’t live up to VA standards,” Cashour said.

Lawmakers from both sides of the aisle, however, have raised questions about VA’s implementation of the law. Criticisms have ranged from the department focusing overwhelmingly on low-ranking staff to the inconsistent and arbitrary enforcement.

Sayers is seeking to be reinstated to his old position, with backpay.