In the field of constitutional law, judicial review gives the power to the courts to examine the actions of all three branches of power in parliamentary democracy - judicial, executive and legislative, and to see if those actions are in consistence with the constitution. In the United States of America, the Supreme Court is in charge of determing whether regulations or laws follow the word of Constitution.
If there are inconsistencies with the Constitution, actions are declared unconstitutional and are therefore, annulled.