Sen. Elizabeth Warren (D-MA), a presumptive 2020 Democratic presidential candidate, is asking ethics officials to examine whether acting White House chief of staff Mick Mulvaney violated federal law by pursuing a job as the president of the University of South Carolina.

Provisions of that law, the Stop Trading on Congressional Knowledge (STOCK) Act, “are designed to stop officials from using their positions to benefit potential employers in order to increase the likelihood of obtaining post-government employment,” Warren wrote in a letter on Tuesday to ethics lawyers for the White House Office of Management and Budget, where Mulvaney still serves as director, and the Consumer Financial Protection Bureau, which he led until December.

The rules at issue bar senior federal officials from “directly negotiat[ing]...any agreement of future employment or compensation” without notifying their agencies’ ethics officers in writing within three days.

Public copies of Mulvaney’s daily schedule at OMB show he was in touch with USC leadership shortly after assuming the post. On March 30, 2017, he met with current USC president Harris Pastides and Steven Beckham, the university’s lobbyist in Washington. The schedule did not list details about their discussion.

“Mr. Mulvaney is one of the top officials in the Trump Administration,” Warren wrote in her letter. “His compliance with the STOCK Act is crucial to protecting American taxpayer and maintaining public confidence in the integrity of the federal government.”

The White House did not respond to a request for comment on her letter.

The New York Times reported this month, citing four sources familiar with the matter, that Mulvaney, then the head of both CFPB and OMB, reached out to a senior official at USC to explore the possibility of replacing the school’s outgoing president.

At the time, White House spokesman Hogan Gidley said that Mulvaney was “is focused on faithfully executing the job the president has asked him to do, and as such he is not interested in any other positions.”