THE BUSINESS arrangement between Billy Carter and the Libyan government, and his prolonged refusal to disclose it, are tawdry. They may also constitute one of the slickest examples of wile in recent times. The only thing certain at the moment is that Billy took $220,000 from the Libyans and his brother is, once again, personally and politically embarrassed.

How much of this deal falls into which category -- greed or wile -- depends partly on the ethical standards by which presidential relatives are judged. It is hard to believe that Billy Carter has had any influence on foreign policy, energy policy or any other policy in which the government is involved. His reputation was in decline even before his contacts with the Libyans began, and his brother had done about as much as he could to dissociate himself from a close relative. In any event, warning flags had gone up all over the place at the moment Billy showed up nearly two years ago escorting some of Libyans around.

It is equally hard to believe that anyone could have thought he had any influence to peddle. It takes a state of mind that puts high value on blood relationships -- not to mention a complete ignorance of presidential history -- to think a man has influence solely because he is the president's brother. Jimmy Carter is not the first president to be plagued by an errant relative. But the Libyans thought Billy had something to offer or, at least, that it was worth investing serious sums of money to find out.

From that perspective, the arrangement that developed must make some of the good ol' boys snicker. Billy took the Libyans (or, more likely, they took themselves) for a good piece of change. All they seem to have gotten in return is some bad publicity, although there is Billy's claim that he "arranged" for a Libyan official to appear on two television shows.

That's a shoddy deal for anyone, and it's truly shabby when the perpetrator is the president's brother. But all that tells you is something almost everyone already knew -- Billy Carter's standards of propriety aren't quite what they ought to be.

The Justice Department's handling of the matter is something else. Its investigation dragged on for months while Billy Carter floated around as an unregistered and, thus illegal foreign agent. He might have been prosecuted rather than merely forced to register. But prosecutions under this law are rare, and government lawyers thought the chances of winning a conviction were not high. Billy Carter did not act surreptitiously in trying to help the Libyans, and the lawyers believed they would have trouble proving that he willfully violated the law.

That's a close decision and one that was made below the top level of the Justice Department. The Carter administration will no doubt take some criticism for it during this year's campaign. But the record now available suggests the Justice Department's final decision was consistent with its handling of similar cases under this law in recent years, involving people whose name wasn't Carter.