In a 1987 case, Puerto Rico v. Branstad,[3] the court overruled Dennison, and held that the governor of the asylum state has no discretion in performing his or her duty to extradite, whether that duty arises under the Extradition Clause of the Constitution or under the Extradition Act (18 U.S.C. § 3182), and that a federal court may enforce the governor's duty to return the fugitive to the demanding state.[4] There are only four grounds upon which the governor of the asylum state may deny another state's request for extradition:[5]

the extradition documents facially are not in order;
the person has not been charged with a crime in the demanding state;
the person is not the person named in the extradition documents; or
the person is not a fugitive.

There appears to be at least one additional exception: if the fugitive is under sentence in the asylum state, he need not be extradited until his punishment in the asylum state is completed.[6]