Done, made, or formulated after the fact.
Example:
Most of Carl's so-called reasons are merely ex post facto excuses for impulsive behavior.
Ex post facto is Latin for "from a thing done afterward." Approval for a project that is given ex post facto -- after the project already has been begun or completed -- is mainly given to save face. An ex post facto law is one that criminalizes an action after it was committed, even though the action was not a crime at the time that it was committed.