High Quality Content by WIKIPEDIA articles! Procedural law or adjective law comprises the rules by which a court hears and determines what happens in civil lawsuit, criminal or administrative proceedings. The rules are designed to ensure a fair and consistent application of due process (in the U.S.) or fundamental justice (in other common law countries) to all cases that come before a court. The substantive law, which refers to the actual claims and defenses whose validity is tested through the procedures of procedural law, is different than procedural law.