Congress enacts Administrative Procedure Act reforms, establishing arbitrary-and-capricious review as the standard for invalidating federal agency rules

The Administrative Procedure Act of 1946 established that federal courts could set aside agency action found to be "arbitrary, capricious, an abuse of discretion, or otherwise not in accordance with law." The Supreme Court's 1983 decision in Motor Vehicle Manufacturers Association v. State Farm reinforced that agencies must give reasoned explanations for their decisions and cannot change course without justifying the shift. This standard became the primary legal tool for challenging agency immigration rules.