motion is not entirely insulated from attack. When the govern ment flatly promises in the plea agreement to make a substantial assistance motion, bargaining away its discretion, “[t]he government then is obligated to make the motion” unless the government can prove by a preponderance of the evidence that the defendant breached the plea agreement. Benjamin, 138 F.3d at 1074. When the government retains its discretion, the district court’s review of a decision not to file is extremely circumscribed, as “a district court may only review the government’s refusal to make the motion to determine whether the refusal is based on unconstitutional considerations, such as the defendant’s race.” Id. at 1073; see also Wade v. United States, 504 U.S. 181, 186, 112 S.Ct. 1840, 118 L.Ed.2d 524 (1992) (<HOLDING>); United States v. Igbinovia, No. 01-5878, 2003
recognizing that a defendant may appeal a district courts refusal to depart downward if the sentence was imposed in violation of law because the district court misconstrued its authority to depart holding that the district courts refusal to grant a downward departure was discretionary and not because it believed it lacked the authority to depart where the court assessed the facts of the case and concluded that the departure requested does not seem  to have a basis holding in the context of a motion for substantial assistance that federal district courts have authority to review a prosecutors refusal to file a discretionary motion  if they find that the refusal was based on an unconstitutional motive such as the defendants race or religion holding that we may not review a district courts refusal to grant a downward departure unless the court mistakenly believed that it lacked the authority to grant such a departure recognizing that federal district courts have the authority to grant a remedy if the refusal to file a substantial assistance motion was based on an unconstitutional motive