• Vietnam War and Cold War spy scandals caused Congress to reassert its power over foreign affairs in 1970s
• War Powers Act of 1973 limited presidents' power to deploy troops without receiving an official act of war from Congress
• In recent years, War on Terror has tested limits of executive power in times of international crisis

Eventually, Congress would decide that this trend had gone too far. A series of revelations about CIA covert operations during the late 1960s and early 1970s (assassination attempts against Cuba's head of state and secret assistance to anti-government plotters in Chile, to name a couple), led Congress to pass new legislation requiring that the CIA make periodic reports to a Congressional intelligence committee. These efforts to restrict the CIA were part of a larger attempt to rein in the presidency. And it was not just the president's foreign policy powers that raised concerns. President Richard Nixon's impoundment of federal monies (that is, his refusal to spend Congressional appropriations with which he disagreed), and his claim that he did not need to answer a court order because he possessed "executive privilege," led many to argue that the president's domestic behavior was also out of control. But it was in the area of foreign policy that these critics of executive power voiced their greatest concerns—in particular, Nixon's continuation of the war in Vietnam without a formal declaration of war from Congress led some to bewail the rise of the "imperial president."

Since the early 1960s, Presidents Johnson and Nixon had waged war in Vietnam without securing a formal congressional declaration of war. Both presidents claimed that the imprecisely worded Tonkin Gulf Resolution of 1964 provided them with the congressional authorization that they needed. But Congress disagreed—and so in 1973, it passed the War Powers Act in order to prevent future presidents from engaging in undeclared military conflicts. Under the act's terms, the president is required to notify Congress within 48 hours of deploying troops "into hostilities or into situations where imminent involvement in hostilities is clearly indicated by the circumstances."⁷ This triggers a 60-day clock during which the president has the authority to use these troops without any further congressional authorization. But at the end of that period, if Congress has not passed a resolution extending their deployment, these troops must be withdrawn. Moreover, if Congress wants the troops removed before the 60 days expires, it can pass a joint resolution demanding their immediate withdrawal.

The War Powers Act remains controversial. Some suggest that it leaves the president too much power to commit troops into war-provoking conditions where Congress has little choice but to continue to fund them. Others say that it unduly ties the president's hands and that it amounts to a de facto (and unconstitutional) congressional veto; that is, by forcing the president to remove troops that he has legally deployed, Congress is exercising a power to cancel or veto presidential action that is not delegated by the Constitution.

And while both Presidents George H.W. Bush and George W. Bush sought Congressional authorization for their military activities in the Persian Gulf, every president since 1973 has suggested that, if push came to shove, they would ignore the War Powers Act and let the Supreme Court finally decide the constitutionality of the legislation.

The debate over the War Powers Act reminds us that the presidency continues to evolve. More recently, Congress and members of the general public have argued that measures to combat international terrorism taken by the administration of George W. Bush represent unconstitutional extensions of the executive office. These critics add that these were just part of a larger strategy of stretching—and perhaps violating—the constitutional limits of the presidential office.

Among their criticisms of the president was his extensive use of "signing statements" to circumvent the purposes of congressional legislation. Since the mid-1980s, presidents have routinely attached a statement to a bill when they signed it into law, explaining some of their reservations about the bill or the interpretations that they would bring to the bill's implementation. President George H.W. Bush attached statements questioning portions of 232 laws; President Bill Clinton challenged 140 statutes. But President George W. Bush made far more extensive use of these statements; he issued close to 700 during his first term alone.⁸

What President Bush's critics found most frustrating was that he made such extensive use of the constitutionally ambiguous signing statement rather than the constitutionally prescribed veto. That is, during his first term of office, the president did not veto a single law; moreover, in many cases, , he supported the negotiations that led to the passage of a complex bill. But then he utilized a signing statement to identify those portions that he believed were problematic, and therefore would not be enforced.For example, when Congress passed laws stating that American troops could not be used to fight drug traffickers in Columbia, Bush's signing statement declared that he would ignore this provision as it violated his prerogatives as commander-in-chief. And when Congress passed "whistle-blower" protections—laws forbidding the executive branch from firing or punishing federal employees who reported possible illegalities to congressional oversight committees—President Bush claimed the right to ignore these provisions as they encroached upon his powers to appoint and remove branch employees.

Congress complained that these signing statements violated its fundamental law-making authority under the Constitution. And in 2006 the American Bar Association joined Congressional critics in condemning President Bush's practice as "contrary to the rule of law and our constitutional system of separation of powers." The ABA added that "the misuse of presidential signing statements by claiming the authority… to disregard or decline to enforce all or part of a law the president has signed, or to interpret such a law in a manner inconsistent with the clear intent of Congress."⁹