The APA supplies a default cause of action and standard of review for challenging federal agency conduct when no other statute governs. It authorizes a court to compel agency action unlawfully withheld or unreasonably delayed, and to set aside agency action found to be arbitrary and capricious, contrary to law, in excess of statutory authority, unconstitutional, or unsupported by the required record.

Review under the APA is typically confined to the administrative record the agency compiled when it acted, not a fresh evidentiary record built through discovery, which distinguishes APA litigation procedurally from ordinary civil litigation. A plaintiff generally must show a final agency action and satisfy standing, and the case is usually resolved on cross-motions for summary judgment rather than trial, since the court is reviewing the agency's reasoning rather than finding facts anew. Remedies are typically limited to vacating the action, remanding to the agency for further explanation, or compelling delayed action — not damages.

A Juricratic simulation of an APA challenge models the standard-of-review dial (arbitrary-and-capricious versus a more deferential or more searching standard depending on the claim type) as one of the most outcome-sensitive inputs in the whole matter, since the same administrative record can support very different projected trajectories depending on how deferential the applicable standard is.

Counsel challenging federal agency action typically confirms finality and standing first, then builds the case around the existing administrative record rather than new discovery, framing arguments around the specific statutory or constitutional defect — procedural, substantive, or both — that the requested standard of review is designed to catch.