What to Know Pennsylvania AG Josh Shapiro filed an Amicus Brief to block the appointment of Acting Attorney General Matthew Whitaker.

The brief argues that Whitaker's appointment is unlawful and ignores vacancy succession statutes.

Democrats have criticized Whitaker's appointment and are concerned about his past criticism of Robert Mueller's Russia investigation.

Pennsylvania Attorney General Josh Shapiro filed an Amicus Brief to challenge the Trump Administration’s appointment of Matthew Whitaker as Acting Attorney General of the United States.

Shapiro and Washington D.C. Attorney General Karl Racine filed the brief with the United States District Court for the District of Maryland in Baltimore on behalf of a coalition of 15 Attorneys General.

Shapiro’s brief argues that Whitaker’s appointment is unlawful, ignores vacancy succession statutes and violates Congress’ controlling statutory designation of the Deputy Attorney General as the Acting Attorney General.

“The naming of Matthew Whitaker as Acting Attorney General is unlawful, and his appointment threatens the legitimacy of the Department’s actions and its vital relationship with the States,” Shapiro said. “I’ve filed in court to protect Pennsylvania’s interests and immediately prevent actions of an illegitimate Attorney General whose decisions could be invalidated.”

Whitaker's appointment has been criticized by Democrats who have challenged its constitutionality and are concerned that he will interfere with special counsel Robert Mueller's Russia investigation.

Deputy Attorney General Rod Rosenstein, the second-ranking Justice Department official, had been overseeing the special counsel's Russia investigation until Whitaker's appointment. Whitaker is now overseeing the investigation.

Democrats have said they are concerned about Whitaker's past criticism of the Mueller probe, which is looking at Russian interference in the 2016 election and ties to Trump's campaign.