Metrorail and the Commuter Corporation, as organs of state exercising public power and providing a monopoly public service under the Legal Succession to the South African Transport Services Act, bear a positive public law obligation to ensure that reasonable measures are in place to provide for the security of rail commuters. This obligation arises from sections 15(1) and 23(1) of that Act, interpreted in light of sections 7(2), 8(1), 10, 11, and 12 of the Constitution and the constitutional value of accountability. The obligation is to ensure reasonable measures are in place, assessed contextually, taking into account factors including the nature of the duty, the social and economic context, the gravity of threats to fundamental rights, and demonstrated (not merely asserted) resource constraints. The existence of a primary responsibility on SAPS under section 205 of the Constitution does not absolve Metrorail and the Commuter Corporation of their complementary obligation to fill any void created by SAPS resource constraints. The Constitutional Court has jurisdiction under section 167(3)(b) to determine disputes of fact on appeal where those disputes constitute issues connected with decisions on constitutional matters, and the Court is not bound in such circumstances by the SCA's application of the Plascon-Evans rule on motion proceedings. Public law obligations of the kind identified do not automatically give rise to delictual duties, which must be determined through trial proceedings where appropriate. Declaratory relief is appropriate and flexible constitutional relief which can clarify legal obligations while respecting the roles of other branches of government in determining how best to fulfill those obligations.