Final answer:
John Marshall ruled that the legal right to commissions was established by Senate approval, the President's signature, and the official seal. The delivery was merely administrative. The point supported Marbury's right but also led to the establishment of judicial review by declaring part of the Judiciary Act of 1789 unconstitutional.
Step-by-step explanation:
In the Marbury v. Madison case, Chief Justice John Marshall emphasized that the necessary actions to make the commissions legal were the approval by the Senate, the President's signature, and the addition of the official seal by the Secretary of State. The delivery of the commissions was an administrative step, but the legal right to the positions took effect once the aforementioned official actions were completed.
This point was important because it addressed the crux of the conflict: Marbury's entitlement to the commission he had been granted. However, while the Court found Marbury entitled to his commission and that James Madison's refusal to deliver it was illegal, it also ruled that it lacked the authority to issue a writ of mandamus ordering Madison to do so. This was because the provision in the Judiciary Act of 1789, which had given the Court the power to issue such orders, expanded the Court's original jurisdiction beyond that granted by the Constitution, and was therefore unconstitutional. The case established the fundamental principle of judicial review, solidifying the power of the Supreme Court to nullify laws that conflict with the Constitution.