The president’s personal lawyers have teamed up with attorneys for other individuals embroiled in Special Counsel Bob Mueller’s probe, multiple sources tell The Daily Beast. For a while, the president’s lawyers even had regular conference calls with other attorneys to discuss the Mueller investigation, according to one source familiar with the calls.

The arrangement is known as a joint defense agreement, and it allows the lawyers to share information—without violating attorney-client privilege. It’s a common strategy when multiple defendants are dealing with the same prosecutor on the same matter.

Joint defense agreements often annoy prosecutors since they let people being investigated share information and compare notes on what the government is doing.

“It gives the defendants an advantage,” said Sol Wisenberg, a criminal defense attorney with the firm Nelson Mullins. “It allows them to know more about what’s going on in the investigation.”