Fourth Amendment to the US Constitution:
"The right of the people to be secure in their persons, houses, papers, and effects, against unreasonable searches and seizures, shall not be violated, and no Warrants shall issue, but upon probable cause, supported by Oath or affirmation, and particularly describing the place to be searched, and the persons or things to be seized."

On 16 December, the New York Times reported that Pres. Bush had ordered the NSA to eavesdrop on American citizens' international communications, without judicial review, in terror cases.

Judge James Robertson —one of eleven members of the secret tribunal that hears cases related to the Foreign Intelligence Surveillance Act (FISA) and its sanctioned investigations— has resigned his post in protest. Judge Robertson reportedly told associates he believed Pres. Bush's order to the National Security Agency (NSA) to spy on Americans may violate federal law.

Though Judge Robertson gave no official reasons for his departure in his letter of resignation, Washington Post writers Carol Leonnig and Dafna Linzer reported on 21 December that "two associates familiar with the decision" report his concern that "warrantless searches" —which underwent no judicial review— "may have tainted the FISA Court's work".

It is not a light concern raised by Robertson's resignation: if reports of his reasons are true, it means that a top member of the federal judiciary believes the extrajudicial searches and eavesdropping executed by the NSA at the president's order undermined the constitutional separation of powers and protection against "unreasonable search and seizure".

The US Constitution is structured specifically to create a system of checks and balances, meaning that the power of any of the three branches of government is limited and counterbalanced by the powers of the other two. The executive branch is given no authority to make law under the constitution and its enforcement of any and all legislation can and must be subject to judicial review, wherein the courts are empowered to provide official and binding interpretation of federal law.

The NSA domestic spy program appears to be rooted in the White House's assertion (already rebuffed by the Supreme Court in a Guantánamo-related case) that the president retains in his own person, under the Constitution, near absolute discretion to interpret, apply, modify and enforce laws, without any oversight by either Congress or the courts.

As a matter of textual fact, there is no such power conferred on the president in the text of the Constitution or in any of its amendments, and no federal law provides such a power to the president. Critics and legal experts have said the assertion of absolute wartime discretion is solely an "opinion" of the president and must, under the Constitution, be tested before a court of law. [s]