Gregory Katsas, a deputy in the White House counsel’s office, said Tuesday he advised the Trump administration on many of the issues that may come before the court he’s nominated to sit on.

Katsas has spent nine months working as a lawyer for President Donald Trump, who nominated him last month to fill the only vacant spot on the U.S. Court of Appeals for the D.C. Circuit. During a Senate Judiciary hearing on his nomination, senators grilled Katsas about which of Trump’s actions he provided legal advice on and his involvement in the ongoing investigation into the Trump campaign led by special counsel Robert Mueller. Katsas in turn gave senators a glimpse into the inner workings of the White House counsel’s office.