A federal judge in Washington on Monday questioned why Justice Department prosecutors failed to turn over favorable information to defense lawyers in a high-profile international drug trafficking conspiracy case.

Monday morning Justice Department prosecutors moved to dismiss without prejudice conspiracy charges against Zhenli Ye Gon, citing “evidentiary concerns” and insisting that prosecution was better suited to unfold in Mexico. Ye Gon faces charges in Mexico that include organized crime and importation of psychotropic chemicals. The prosecution also moved to dismiss an accompanying criminal forfeiture allegation.