A STRANGE DISPUTE has developed in the Microsoft antitrust litigation between the software giant and Judge Thomas Penfield Jackson over a law professor named Lawrence Lessig. Two years ago, Judge Jackson sought to appoint Mr. Lessig -- a noted expert on Internet-related legal issues -- to serve as a special master in the case. Microsoft objected both on legitimate procedural grounds and on the specious suspicion that Mr. Lessig was biased against the company. Though Microsoft eventually won at the court of appeals on the question of whether Mr. Lessig had been -- for purely procedural reasons -- improperly appointed, the vehemence of the company's attack on him remained one of the uglier moments of the early phase of the litigation.

Judge Jackson, it turned out, wasn't done trying to get Mr. Lessig into the case -- and Microsoft wasn't done trying to keep him out. The judge, in an unusual move, recently invited him to submit a friend-of-the-court brief in the case, and Microsoft promptly objected again.

The company's contention that Mr. Lessig is too biased to file such a brief is quite unfair. The attack on Mr. Lessig two years ago was based on some joking and stray comments he made about the company in e-mail messages and his participation in seminars with Microsoft critics. The company's recent objections have been stated more mildly, but they are -- as Judge Jackson noted in rejecting them -- no more merited. The company notes Mr. Lessig's membership on the advisory board of a nonprofit group sponsored by a Microsoft competitor called Red Hat. The idea that such matters would disqualify Mr. Lessig from writing a brief seems quite strained -- and one wonders why the company is so eager to cast aspersions on the man.

At the same time, the judge's position in this matter is peculiar too. Though Judge Jackson probably has the authority to seek Mr. Lessig's views, his strenuous efforts to bring the professor into litigation where he has no direct interest creates an appearance that he is looking to Mr. Lessig to resolve the case for him. "The Court suspects that there may be valid legal analyses . . . which would comport fully with neither position likely to be taken by the parties, but which the Court itself might find more consistent with the public interest," he wrote in rejecting Microsoft's objection to Mr. Lessig. "It was in anticipation that Professor Lessig might offer just such an analysis that the Court extended the invitation to him to appear as amicus curiae."

Having been denied Mr. Lessig as a special master, in other words, the judge seems to be nonetheless all but openly asking the professor how he should rule in the case. But Mr. Lessig -- however crass the attacks on him have been and however fine a scholar he is -- cannot serve as a surrogate judge. Judge Jackson should be wary of language that seems to cast him in that light.