The National Mall in Washington, D.C., is America’s front yard, or so the saying goes. The museums and special events draw some 25 million visitors a year. With that much foot traffic, and a longtime congressional policy of deferred maintenance, it should come as no surprise that these days the Mall looks less like a manicured lawn and more like a back alley.

So it would seem like a good thing that U.S. secretary of the interior Ken Salazar and national park service director Jon Jarvis unveiled an improvement plan for the Mall last November. But ironically, their good intentions have undermined one of the government’s most important sustainable-design initiatives. Salazar and Jarvis’ plan has yet to be funded or scheduled, yet in early January the Park Service used it as an excuse to revoke the Solar Decathlon’s permit to use the Mall this fall.

The biennial Decathlon is an initiative of the U.S. Department of Energy, in which teams of students from universities around the world design technologically sophisticated green model homes. Every other fall, the homes are erected on the Mall and opened for viewing.

The program has proved its worth on many levels: Students gain hands-on experience, manufacturers a rigorous testing ground, and the public and policy makers an object lesson about architecture’s vast capacity to save energy and help the environment. Four successive Decathlons have occurred on the Mall, on the axis between the Capitol and the Lincoln Memorial. But no longer.

For a while, bloggers circulated a rumor that the Decathlon would move to a parking lot at National Harbor, a mixed-use development located miles away from the Mall in Maryland—or even to another city altogether.

Finally, on Feb. 24, the Park Service backtracked slightly and granted permission for the Decathlon to take place at West Potomac Park, on a spit of land between the Potomac River and the Tidal Basin just north of the Jefferson Memorial. Technically the new site is part of the Mall, but in reality it is too far from downtown Washington, D.C., and has far less symbolic resonance than the original location.

The Association of Collegiate Schools of Architecture (ACSA) is understandably outraged. “West Potomac Park does not equal the National Mall,” says ACSA president and University of Washington architecture dean Daniel Friedman. “The success and stature of the Solar Decathlon program reflects the kind of visibility only the National Mall can provide.” ACSA even suggested making post-event site restoration a requirement for participants. To no avail.

I find it unconscionable that the Park Service, a steward of America’s natural environment, allows celebrities such as Glenn Beck and Jon Stewart to stage massive rallies on the Mall while eighty-sixing an educational program that exemplifies the Obama administration’s clean-energy goals. Meanwhile, the Park Service has permitted the Library of Congress to use the Mall for its 2011 National Book Festival, an event that attracts more than 100,000 people, during a weekend previously reserved for the Decathlon. The logic of all this escapes me.

It’s difficult to argue against the need to restore dignity to the Mall in the form of improved maintenance and services. The grass should be green and healthy, and the restrooms plentiful. But why should those goals preclude active use of the space, by real, live human beings, especially when they promise to clean up after themselves? The Mall is lined with museums whose guiding principle is “look, don’t touch.” The Mall, by contrast, should operate in an aggressively hands-on fashion, in keeping with the inclusive design of the American republic.

Since architect Pierre L’Enfant drew up his “Plan for the City of Washington” in 1791, the Mall and its uses have evolved dramatically, in keeping with changing necessity, resources, design trends, and definitions of national identity. But in recent years the Park Service, the National Capital Planning Commission, and other groups have adopted an essentially reactionary position where the Mall is concerned, attempting to lock it into its current configuration—the fewer changes, the better.

Where’s the value in rewriting history, in saying that the Mall in its current form is how the Mall always has been, and always should be? It’s like arguing that the U.S. Constitution doesn’t need amendments. The Mall deserves a noble, vibrant future, not prescriptive preservation in a fictitious historical condition.

The Park Service plan reflects this limited vision. Out of a $600 million budget, 75 percent will go to repairs. The repairs are necessary, but so too are amendments—many of them, over time, in the form of spirited events, art, and architecture. The Mall may be sacred ground, but it shouldn’t be inviolable.

Why not wed the goals of the Decathlon with the Park Service’s requirements for new facilities? The students could be tasked with designing restrooms, band shells, food kiosks, and the like. These improvements could last for months or years, rather than a few weeks. Like America’s great, ongoing experiment in representative government, the innovative architecture of the Solar Decathlon could serve immediate needs on the Mall—and, in the process, excite millions of minds.