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.

In context of procedural law; procedural rights may also refer not exhaustively to rights to information, rights to justice, rights to participation which those rights encompassing, general Civil and Political rights. In environmental law, these procedural Rights have been reflected within the UNECE Convention on "Access to Information, Public Participation in Decision-making and Access to Justice in Environmental Matters" known as the Aarhus Convention (1998).

Although different legal processes aim to resolve many kinds of legal disputes, the legal procedures share some common features. All legal procedure, for example, is concerned with due process. Absent very special conditions, a court can not impose a penalty - civil or criminal - against an individual who has not received notice of a lawsuit being brought against them, or who has not received a fair opportunity to present evidence for themselves.