What was the major effect of marbury vs madison

Established judicial review--the supreme court decided that it had the authority to interpret the US constitution.

The most important effect of this case was on the nature of American government.  The case gave the Supreme Court the power of judicial review.  It allowed the Court to declare laws passed by Congress to be unconstitutional.  Even though this power was not used again for decades, it has come to have a huge impact on the way our country looks today.