Changes to the constitution by means other than formal amendment is called

Judicial Review

Explanation: Judicial review is the power of the courts of a country to examine the actions of the legislative, executive, and administrative arms of the government and to determine whether such actions are consistent with the constitution or not.

Judicial review can also be said to be the adjudication of constitutionality of statutes especially by the Supreme Court of the United States. Judicial review depends upon the existence of a written constitution.

Constitutional judicial review begun with the assertion by John Marshall, the fourth chief justice of the United States (1801–35), in Marbury v. Madison (1803), that the Supreme Court of the United States had the power to invalidate legislation enacted by Congress.