It’s not clear if Trump Jr. will comply with the subpoena, though if he doesn’t it will just further add to the tensions in Washington.

Two congressional sources told Reuters Thursday that Trump Jr. is unlikely to comply with the subpoena and could cite his Fifth Amendment constitutional right against self-incrimination. Sen. Richard Blumenthal (D-Conn.), a member of the Judiciary Committee and former U.S. attorney, argued that the president’s son could be jailed if he tries to invoke executive privilege to avoid testifying.

Some Republicans worry that Burr, who has said he will not run for another term in 2022, is giving Democrats more ammunition by calling Trump Jr. to testify a second time before the Intelligence Committee about Russia’s activities during the 2016 election.