Its not a double negative.  It is saying that a petition right now is worthless.  Pure and simple.
Your only hope is to show that the mayor commited a crime by destroying the field.  Your absolute only hope.  Cause then, to reconcile, you may get funding to rebuild the strip and guarantee the field's survival for a little while longer.
Basically, if the action was legal, you are not deciding on closing a functional strip, you're deciding on what to do with a nonfunctioning one.
MiniD