An aide to Republican Rep. Trey Gowdy, chairman of the House Oversight and Government Reform Committee, says complaints from the Trump transition team about special counsel Robert Mueller should be decided by the court instead of Congress.

Kory Langhofer, the counsel to the Trump for America transition team, accused Mueller of inappropriately obtaining emails related to the transition in a letter to Congress on Saturday.

Mueller “extensively used the materials in question, including portions that are susceptible to claims of privilege,” the letter said.

“The central issues raised are fact specific legal issues which involve issues of privilege, waiver (express, implied, actual and constructive), standing to assert claims of privacy, expectations of privacy and the reasonableness thereof, third party consent, statutory constructions, and inevitable discovery, among other issues. There are issues to be briefed by the parties (or others with cognizable legal claims and standing and decided by the court — not Congress,” the aide told Politico.

Mueller’s team, which is investigating Russia’s meddling in the 2016 election and possible Trump campaign collusion with the Russians, obtained thousands of emails from the transition team from the General Services Administration agency. The GSA hosted the email server of the transition team.

Langhofer said the GSA “did not own or control the records in question” and the release of documents could be a violation of the Fourth Amendment.