 Moreover, the regulation narrowly focuses on the Government's substantial interest in maintaining the parks in the heart of the Capital in an attractive and intact condition, readily available to the millions of people who wish to see and enjoy them by their presence.To permit camping would be totally inimical to these purposes.The validity of the regulation need not be judged solely by reference to the demonstration at hand, and none of its provisions are unrelated to the ends that it was designed to serve.