JUDGE THOMAS Penfield Jackson was wrong in barring Nation of Islam leader Louis Farrakhan and the Rev. George Stallings from attending Mayor Marion Barry's trial last week. Both are controversial current supporters of the mayor to whom he had offered one of his four passes to the proceedings. The judge said he was barring them and unnamed "others who also fit into the same category" for fear that their presence would be "disruptive" and "intimidating." The American Civil Liberties Union is appealing on their behalf and that of the mayor on grounds that keeping them out of the courtroom poses its own risk to a fair trial, greater than any risk in letting them in. The ACLU is right.

The Sixth Amendment to the Constitution guarantees criminal defendants public trials in part precisely so that they can have supporters present, as a kind of check and discipline on the process, including on the jury. One side's intimidation can be another's reminder of the need for fair play. While trial judges are obliged to guard against disruption and have great discretion in doing so, only in the most extreme of circumstances are they allowed to keep out the public or members of it, most especially the defendant's friends. Here the judge held no inquiry but merely announced that the two ministers and others like them would be unwelcome. Which others? "Perhaps you should give me the list so we can save some time," said Kenneth Mundy, the mayor's lawyer. "I think you will know them when you see them," replied the judge.

It's clear enough what the mayor and his lawyers might hope to gain by having Mr. Farrakhan or the Rev. Stallings in attendance. But the jury, though sequestered, cannot be unaware of the strong and divided feelings that exist in the city to which it will return when it reaches its verdict. Nor is Mr. Barry without the right to remind it of such divisions. Mr. Farrakhan stands, among other things, for the proposition that whites -- in this case the government -- will always try to bring strong blacks down. That has been a theme among the mayor's defenders as well. Perhaps Mr. Farrakhan's presence would remind them of that message; had the ministers been admitted they would have sat not at the defense table itself but in the spectator's half of the courtroom, mostly likely on the mayor's side in the front row. But the racial undercurrents of this case are hardly news to the jury, and there is a limit to how far the judge can seal the jury off, or should even try.

In the city at large, the ban, as such things almost always do, has only magnified the issue that in his courtroom the judge was trying to set aside. You don't have to admire Louis Farrakhan or ignore his own abiding contribution to racism to believe that he should not be barred on the grounds cited.