The federal government argued in a brief filed yesterday with the U.S. Court of Appeals that the government's commitment to build a "model shelter" for the homeless was not legally binding and that a lower court judge erred in ordering federal officials to find alternative shelters before closing a shelter operated by the Community for Creative Non-Violence.

The brief was the government's response to an appeal by CCNV of U.S. District Court Judge Charles R. Richey's ruling Aug. 19 that federal officials could carry out a plan to close the shelter at 425 Second St. NW, but not before relocating its residents and devising a long-range plan "to eliminate homelessness in the nation's capital."

Royce C. Lamberth, an assistant U.S. attorney, said the brief included a cross-appeal of Richey's ruling, in which federal attorneys asserted that the judge had stepped outside his jursidiction and should not have imposed the requirement to find alternative shelters.

"We say that when a statement of policy is made by agency officials . . . it was not a legally binding commitment on the government," Lamberth said, in a reference to a statement by U.S. Department of Health and Human Services Secretary Margaret M. Heckler on behalf of President Reagan, committing the government to build a model shelter.

"Even if it was legally binding, it can then be changed because of changed circumstances," he added. "The changed circumstances, we argue, are that CCNV and Mitch Snyder, the group's leader barred entry to the building when we began the repairs because the repairs weren't being done according to their architect's plans."

CCNV has blocked the government's plan to spend $2.7 million to renovate the facility, calling it an abrogation of Heckler's promise, and has held out for a larger-scale plan to renovate the structure.

HHS officials have proposed using 40 trailers to house the estimated 600 residents of the shelter.

Lamberth said that if the three-member appeals court panel, which will hear the case Sept. 26, rules in favor of the government, it "would be free to take whatever action . . . that is deemed appropriate."