How do court decisions supplement a written constitution?

Court decisions supplement a written constitution primarily through the process of judicial review, which allows courts to interpret constitutional principles and determine the validity of legislative or executive actions.12

Because constitutional documents often contain broad or ambiguous language, they cannot anticipate every legal scenario. Courts fill these gaps by applying constitutional norms to specific, concrete cases. Through this process, judges effectively give specific meaning to abstract constitutional provisions, sometimes developing new legal principles—such as the right to personal privacy in the United States—that were not explicitly written in the original text.31

Furthermore, in systems that follow the doctrine of precedent, judicial interpretations become binding rules for future cases. When courts declare a statute unconstitutional, they act as a check on the other branches of government, ensuring that legislative and executive acts remain within the boundaries defined by the constitution. While some countries utilize specialized constitutional courts to provide abstract or advisory rulings, in many systems, this supplementary role is performed by ordinary courts as they resolve actual legal controversies.3124