American administrative law has been rebuilt in the space of a few Terms, and this UpLaw guide maps the federal system as it now stands rather than as the casebooks used to describe it. It begins with the constitutional anxieties that shadow the administrative state (nondelegation, the Appointments Clause, and the removal power), then walks the Administrative Procedure Act's architecture: rulemaking versus adjudication, the mechanics of notice-and-comment under 5 U.S.C. § 553, the exemptions for interpretive rules and policy statements, and the persistent problem of regulation by guidance. It works through the grounds for setting aside agency action in § 706, explains what hard-look review under State Farm actually demands, and traces how reasoned decisionmaking, changed positions, and pretext are policed. It then confronts the central development of the decade: Chevron deference has been overruled, and Loper Bright Enterprises v. Raimondo restores independent judicial judgment on questions of law, leaving Skidmore respect, express delegations, and the major questions doctrine to do the remaining work. It covers agency adjudication and the jury right recognized in SEC v. Jarkesy, the justiciability gauntlet of standing, finality, ripeness, and exhaustion, the limitations rule after Corner Post, and the remedial fight over vacatur and universal relief, closing with a step-by-step campaign plan for challenging a rule. A single invented company, Copperline Battery Systems, carries a challenge through every stage so the doctrine stays concrete, and a currency note flags the areas of the field that are moving fastest.