THE JUSTICE DEPARTMENT made, we suppose, the best deal it could to obtain the testimony of Tongsun Park, the South Korean rice trader indicted for buying influence in Congress.In exchange for his "truthful" testimony and "full cooperation" at a deposition in Seoul and at subsequent trials here, as determined solely by Justice , the department offered him immunity from prosecution. Sure, it would have been preferable to question him out of Korean government hearing, and to take testimony as well from current Korean officials, including the two past ambassadors to Washington and the former director of the Korean CIA. But Justice did manage to move the stalled influence-buying inquiry off the dime.

Leon Jaworski, special counsel to the House ethics committee, protest that Justice did not get Mr. Pak to testify before a grand jury (that is, out of Korean government hearing). True. He's unhappy that Mr. Pak is not required to answer questions about present Korean official. True, but we not a promising loophole. This ban does not apply if the involvement of the officials occurred in the United States or in the presence of American officials. Mr. Jaworski also criticizes the Justice Department for suggesting that the Congress content itself with a transcript of the Seoul deposition. True, but the Justice-Tongsun Park agreement will bring the Korean to this country, where it will be possible - with his agreement, his attorney says - for Congress to take his testimony.

It has to be kept in mind that Justice and Congress have very different aims. justice wants to make criminal cases. Congress and its members want, or so we still presume, to demonstrate that they are as vigilant in policing - and disciplining - themselves as they must see not only that no member broke a law but also that no member violated Congress's own ethical standards. They must demonstrate, in the end, a willingness to bring their own members to book for violations of the rules, and for censure or even expulsion if such punishment is warranted. There may be only a "handful" of fresh indictments (and none of sitting congressmen), the Justice Department now says. But Rep. Bruce Caputo (R-N.Y.), who sat in on the opening sessions of the Park deposition, says that "dozens and dozens" of congressmen were touched in some way by the influence-buying scandal.

This is the monkey on Congress's back. It is a diplomatically embarrassing fact, but a fact no less, that Congress can't get rid of theat monkey unless Seoul cooperates. Congress has the power - in its direct control over aid funds and its indirect control over the whole climate in which Korean-American relations are conducted - to bargain for further testimony by other Koreans, even by present officals, if thet proves necessary. We read Mr. Jaworski's complaints not so much as an attack on the Justice Department as a signal to South Korea that it cant get away merely by producing Tongsun Park.