Drawing a capacity crowd of onlookers, the Carter administration went before the U.S. Court of Appeals here yesterday to seek a reprieve for its heavily battered wage-price guidelines program.

Contending that the program is voluntary and hence legal, Deputy Attorney General Benjamin R. Civiletti asked the court of overturn U.S. District Court Judge Barrington Parker's decision last month that economic sanctions, in effect, turn the guidelines into mandatory controls.

Parker ruled that President Carter exceeded his consitutional powers in threatening to deny federal contracts to guideline violators because Congress had never, implicitly or explicitly, authorized such action.

Parker enjoined the government from imposing the sanctions but stayed enforcement of his order pending the appeal.

Civiletti's appearance to argue the government's case - and the crowd that was drawn to hear it - underscored the important the administration attaches to the appeal. Parker's decision deprived the government of its main enforcement penalty, leaving it only with its powers of persuasion, which have brought only modest results thus far.

In arguing that the nine-member appeals court unhold Parkerhs ruling, lawyers for the AFL-CIO and 24 Republican members of Congress, who banded together to fight the guidelines sanctions, reiterated their arguments that Carter had acted without legal authority.

Moreover, they said, the authority the government claims is so broad and open-ended that it envisions no limits to the kind of economic controls a president could impose.

Civiletti argued that Congress, through the 1949 Procurement Act, delegated to the president the prerogatives of any "prudent buyer" in purchasing goods and services - which, he said, Carter was doing in his executive order requiring guidelines comliance for doing business with the government.

It would be "tragic, even ludicrous" for the administration to urge others to hold won costs while it is restrained from doing so itself, he said.

In their questioning, the judges indicated some concern over whether the contract denial penalty makes the guidelines mandatory and hence illegal.

At one point, Judge Harold Leventhal said he did not see where there is any "legal duty" to comply with the guidelines, suggesting the program may thus be less than mandatory. But when Civiletti suggested that penalties such as fines define the difference between mandatory and voluntary programs, Judge Roger Robb questioned the relative severity of a $10,000 fine or a loss of $1 million in government contracts.

The court gave no indication when it will rule, although it has given the case priority treatment thus far. The full court, rather than the customary smaller panel, heard the case on an expedited schedule only 13 days after Parker's ruling.