THE PROPER LINE between the public life and the private affairs of high government officials is often difficult to draw. But one thing, at least, is clear. It is that a government official must never use his office to gain favors that may benefit his own financial interests or those of his friends. Since it is almost impossible for a high official to divorce himself from his office, this greatly limits the things he can do legitimately to protect his own financial position.

Now let's see how this general principle applies to the situation of Assistant Secretary of Agriculture Robert H. Meyer. He and his family own or are buying a large amount fo farm land in the Imperial Valley of California. He is appalled by a recent decree of the Interior Department, and he believes he may be threatened with bankruptcy if it goes into effect, forcing him to sell more than half the land. He believes that decree is legally and morally wrong. And he knows it will hurt his neighbors and friends as well as himself. What can he do about it?

What Mr. Meyer did was raise that question with Agriculture Secretary Bob Bergland. Mr. Meyer says he was told not to get involved officially in the controversy over the decree, but he understood he was also told that there was no objection to his speaking about the problem in his own behalf as a private citizen. Subsequently, he helped arrange meetings for two neighbors, one of them the administrator of his own land trust, with several congressmen and high Interior Department officials. He apparently also discussed the matter with White House officials. It is said that he tried hard in all these activities to make clear that he was acting as a citizen and not as an assistant secretary.

While we sympathize with Mr. Meyer's problem, we think what he did was wrong. It shows a lack of sensitivity to the principles that underlie the rules about conflicts of interest. You can attribute it to naivete, as do high Department of Agriculture officials who claim Mr. Meyer misunderstood what Secretary Bergland told him. But there is no need to call in the lawyers, as the Secretary has done, to see if any specific law of any directive of the President has been violated. What Mr. Meyer has done is to obtain access to high officials who might otherwise not have been accessible for those who can speak about the Imperial Valley problem. Since the problem affects him directly, that is using public office to protect one's financial interests. There is almost no way an assistant secretary of anything can ask as member of Congress for a personal favor without getting in the position of owing a favor in return. And if Secretary Bergland, who is an old congressional hand, didn't make that clear to Mr. Meyer, we fault the Secretary, too.

What could Mr. Meyer have done legitimately? The real evils against which conflict-of-interest principles are aimed are secrecy and favoritism. Therefore, Mr. Meyer could have appeared publicly before a congressional committee to testify, as a private citizen and not an assistant secretary, against the Interior Department plan. (That, incidentally, would have been a good test of the Carter administration's tolerance of internal dissent.) Or he could have written letters aginst it, again as a private citizen, as long as the letters became public knowledge or part of a public record. All citizens have the right to do those things, and they do not lose it by becoming public officials. But they do lose the right other citizens have to lobby for their personal interests, and they cannot lend the prestige of their office to others who will lobby for it.

Maybe the best course for Mr. Meyer to pursue now is to resign and become the chief lobbyist before Congress for himself and his friends and neighbors. The Imperial Valley question is not a simple one, and there is considerable validity in the position he takes. He could certainly be an eloquent spokesman for his point of view.

Beyond that, however, we are troubled by the way the Department of Agriculture has handled this matter. If Mr. Meyer was as naive about the ways of Washington as its officials now contend, he was entitled to considerably more guidance that he got. If he wasn't, the view about conflicts of interest at high levels of that department is sloppy, to put it kindly. Either way, the President's bold promises about clean and good government have to be taken more seriously by his own administration if they are to have any value at all.