When the Supreme Court declares a law that was created by congress unconstitutional its an example of

I believe it is an example of check and balances. Checks and balances, principle of government under which separate branches are empowered to prevent actions by other branches and are induced to share power. They are applied primarily in constitutional governments. The system of check and balances is used to keep the government from getting too powerful in one branch. For example, the Executive Branch can veto bills from the Legislative Branch, but the Legislative Branch can override the veto.