A federal judge on Friday dismissed former Trump campaign chairman Paul Manafort’s lawsuit challenging special counsel Robert Mueller’s power, ruling that his civil case was not the “appropriate vehicle for taking issue with what a prosecutor has done in the past or where he might be headed in the future.”

Manafort sued the U.S. Department of Justice in January, arguing that the special counsel had gone beyond its mandate of investigating Russian interference in the 2016 presidential election by probing his overseas lobbying work. The lawsuit, filed in Washington federal district court, came three months after Manafort and his longtime associate Rick Gates were indicted on criminal charges related to their past lobbying work for Ukraine.