the court's work." Judge Richard Posner opined that FISA "retains value as a framework for monitoring the communications of known terrorists, but it is hopeless as a framework for detecting terrorists. [FISA] requires that surveillance be conducted pursuant to warrants based on probable cause to believe that the target of surveillance is a terrorist, when the desperate need is to find out who is a terrorist." Related issues Earlier warrantless surveillance The Bush administration compared the NSA warrantless surveillance program with historical wartime warrantless searches in the US, going back to the time of the nation's founding. Critics pointed out that the first warrantless surveillance occurred before the adoption of the U.S. Constitution, and the other historical precedents cited by the administration were before FISA's passage and therefore did not directly contravene federal law. Earlier electronic surveillance by the federal government such as Project SHAMROCK, led to reform legislation in the 1970s. Advancing technology presented novel questions as early as 1985. Executive orders by previous administrations including Presidents Clinton and Carter authorized their Attorneys General to exercise authority with respect to both options under FISA. Clinton's executive order authorized his Attorney General "[pursuant] to section 302(a)(1)" to conduct physical searches without court order "if the Attorney General makes the certifications required by that section". Unitary Executive theory The Unitary Executive theory as interpreted by John Yoo et al., supported the Bush administration's Constitutional argument. He argued that the President had the "inherent authority to conduct warrantless searches to obtain foreign intelligence". The United States Court of Appeals for the District of Columbia ruled that the President's authority as commander-in-chief extends to the "independent authority to repel aggressive acts ... without specific congressional authorization" and without court review of the "level of force selected". Whether such declarations applying to foreign intelligence are or must be in compliance with FISA has been examined by few courts. Classified information Leaks No single law criminalizes the leaking of classified information. Statutes prohibit leaking certain types of classified information under certain circumstances. One such law is ; it was tacked on to the Espionage Act of 1917. It is known as the 'SIGINT' statute, meaning signals intelligence. This statute says: This statute is not limited in application to only federal government employees. However, the Code of Federal Regulations suggests the statute may apply primarily to the "[c]ommunication of classified information by Government officer or employee".