Donald Trump’s Cabinet appointees are not the only source of controversy in his transition back to the White House.

On Thursday, Sen. Elizabeth Warren (D-Mass.) wrote the Administrator of the General Services Administration (GSA), which manages the functioning of federal agencies, to warn that the Trump transition team has refused to sign memoranda of understanding with the Biden-Harris administration. All prior presidents-elect have signed the agreements, which outline how the administrations will work together; one of them, for example, would allow the FBI under the current administration to conduct background checks on Trump’s nominees. Another would facilitate the Trump team’s national security clearances required to receive classified intelligence briefings before he assumes office. “The Trump team’s unprecedented refusal to sign agreements with the outgoing administration threatens the American public by hamstringing incoming officials’ ability to govern responsibly,” Warren writes.

On top of that, Trump’s transition team has yet to publish a full ethics code on the GSA website addressing how he will deal with his conflicts of interest, as required by a law that Trump himself passed in 2020. Warren’s letter notes that while the Trump team has published its own ethics code, “it includes nothing about how President-elect Trump will manage his own extensive financial conflicts of interest—which experts anticipate will be one of the most alarming corruption challenges of the incoming administration.” The refusal to publish the ethics code, Warren says, heightens “the risk of the incoming administration governing for the benefit of special interests rather than the American public.”

As the New York Times reported Sunday, it’s possible these “special interests” could, in fact, be helping to fund the Trump transition: Because the Trump team has not signed a memorandum of understanding with the GSA that was due Sept. 1, they have been able to shield the names of donors to the transition. If the Trump transition had entered into the agreement, they would have to publicly disclose donors, each of whom would have an individual giving limit of $5,000—but the Trump team would have been able to access $7.2 million in federal funds to help with the costs of the transition.

Trump is also reportedly the first president to circumvent this agreement, which seems to suggest his team thinks he can raise more from donors without being limited to the $5,000 cap per individual donor. But as one expert told the Times, it could come at a serious ethical cost:

“When the money isn’t disclosed, it’s not clear how much everybody is giving, who is giving it and what they are getting in return for their donations,” said Heath Brown, a professor of public policy at John Jay College of Criminal Justice who studies presidential transitions. “It’s an area where the vast majority of Americans would agree that they want to know who is paying that bill.”

In her letter to the GSA, Warren asks them to respond by December 5 to questions about how the agency is engaging with the Trump transition and the impacts of the Trump team’s lack of compliance with federal law. Spokespeople for the Trump transition team and the GSA did not immediately respond to requests for comment from Mother Jones on Sunday morning.