WordNet (r) 3.0 (2006):

due process
    n 1: (law) the administration of justice according to
         established rules and principles; based on the principle
         that a person cannot be deprived of life or liberty or
         property without appropriate legal procedures and
         safeguards [syn: due process, due process of law]

Moby Thesaurus II by Grady Ward, 1.0:

19 Moby Thesaurus words for "due process":
   actionability, applicability, constitutional validity,
   constitutionalism, constitutionality, jurisdiction, justice,
   justiciability, lawfulness, legal form, legal process, legalism,
   legality, legitimacy, legitimateness, licitness, rightfulness,
   scope, validity