As The Post knows, protecting the president is a serious matter. Congress has passed laws to enable the secretary of the Treasury, through the Secret Service, to provide for the safety of the president and his family.

The Supreme Court has long recognized the paramount importance attached to protecting the president. In a 1969 decision, Watts v. United States, the Supreme Court stated: "The Nation undoubtedly has a valid, even overwhelming interest in protecting the safety of its Chief Executive." The authority to protect the president has been and must be construed broadly.

Pennsylvania Avenue, State Place and South Executive Avenue are unique in that they are part of the federal enclave known as the National Capital Service Area (as defined in 40 U.S.C. 136) and immediately adjacent to the White House complex. The White House Security Review, an independent team established by then-Treasury Secretary Lloyd Bentsen to examine White House security issues, concluded that there was no other alternative to prohibiting vehicular traffic on these streets that would ensure the protection of the president and others in the White House complex. This recommendation sets apart these streets from any other street in the District. Therefore, The Post's suggestion that this action has implications for other city streets is unwarranted.

The recommendations of the White House Security Review Report convinced Treasury Secretary Robert E. Rubin that immediate action was required. Before taking this action, Treasury officials consulted with various congressional and city officials. To do more would have risked compromising the president's safety. To ensure the smoothest possible transition, the federal government is working with a wide range of officials, including those of the D.C. government.

As many have noted, the restricted access pertains only to vehicles. The White House is still the "People's House," and visitors still can enter it on tour. Protesters still can gather to express their views. Cars still can drive by and get an unimpaired view of the south grounds. Pedestrians, particularly tourists, still can enjoy this historic area, as the last few days have amply demonstrated.

The precautions taken last weekend will not affect the status of the White House as a public institution to be enjoyed by everyone. The only change is the elimination of vehicular traffic from the avenue because of the serious security concerns demonstrated by the Oklahoma City bombing.

Sadly, we live in a changing world. As this week's incident on the South Lawn shows, we must remain ever vigilant. EDWARD S. KNIGHT General Counsel Department of the Treasury Washington