A federal judge on Wednesday appeared reluctant to rein in special counsel Robert Mueller’s investigation into Russian meddling in the 2016 presidential election, a probe that former Trump campaign chairman Paul Manafort has challenged as overbroad for veering into his overseas lobbying business.

Three months after being indicted on criminal charges related to his lobbying for Ukraine, Manafort in January sued the government alleging that Mueller was unlawfully appointed and that his investigation had strayed far from its original mandate of investigating any ties between the Trump campaign and the Russian government.