The right to access to court is long recognised as an essential element of a Union based on the rule of law. This book asks how can member states insure that their individual rules on standing guarantee that right? The book answers the question by analysing EU law's requirements from two angles: first, the effective protection of Union rights; second, the effectiveness of Union law per se. With inductive case law examination, it formulates an autonomous Union law doctrine of standing. The book then goes further, setting out an effectiveness test of member states' enforcement mechanism, preventing practical impediments to the right to access to court. This is a rigorous study on a question of immense importance.