I've read a bunch of these types of articles. Fenty has a duty to defend the laws of DC, not stategize nationally. His fiducial duty is to appeal.
So he has 90 days to make a decision (like give notice they plan to appeal), or to file a brief (in which the decision would need to be made much sooner so the documents can be prepared)?
File a petition for certiorari, which is a brief telling the Court what the case is about and why it is important for the Court to hear the case.