John Adams is telling William Murbary to be a judge in the District of Columbia for the federalist party.
Madison should hand over Marbury's commission, but the Supreme Court doesn't have the power to make that happen. Section 13 of the Judiciary Act of 1789 violates the Constitution.
The commissions weren't delivered when Thomas Jefferson became president, so Jefferson decided to tell James Madison to not deliver them.
Now the court can declare acts of Congress unconstitutional if they exceed the powers given by the constitution!
Okay?
William Murbary got mad at James Madison for not sending in his commission to be a judge, so Murbary sues Madison.
The court is now equal to and independent of Congress and the Executive Branch!
John Marshall is the judge for their case and he decided that Madison should give Marbury his commission. Marshall then states that the Supreme Court doesn't have the power to make that happen. This leads to a chain of events that will change the United States forever.
Because of John Marshall, the court can declare acts of Congress unconstitutional if they exceed the powers that the constitution has given them.
He also made it evident that the court is equal to and independent of Congress and the Executive Branch.