Subsection (b), 28 U.S.C. § 1292, authorizes the courts of appeals to entertain appeals from certain non-final orders entered by the district court (1) if the district court has stated in writing, in the order, that it involves a controlling question of law as to which there is a substantial ground for difference of opinion and that an immediate appeal from it may materially advance the ultimate termination of the litigation, and (2) if permission to appeal is granted by the court of appeals. Upon application within 10 days after entry of the order, the court of appeals may, in its discretion, allow an appeal to be taken. Examples of orders that may be appropriate for appeal under 28 U.S.C. § 1292(b) are those overruling a defense going to the right to maintain the action, such as a challenge to capacity or to jurisdiction; orders refusing to permit joinder of a third-party defendant; and orders transferring cases to other district courts under 28 U.S.C. § 1404 in which the jurisdiction of a transferee court is in issue.

[updated July 2018] [cited in JM 2-2.112]