In what appears to be a first, a U.S. court is forcing a journal publisher to breach its confidentiality policy and identify an article's anonymous peer reviewers.

The novel order, issued last month by a state judge in California, has alarmed some publishers, who fear it could deter scientists from agreeing to review draft manuscripts. Legal experts say the case, involving two warring fitness enterprises, isn't likely to unleash widespread unmasking. But some scientists are watching closely.

The dispute revolves around a 2013 paper, since retracted, that appeared in The Journal of Strength and Conditioning Research. In the study, researchers at The Ohio State University in Columbus evaluated physical and physiological changes in several dozen volunteers who participated for 10 weeks in a training regimen developed by CrossFit Inc. of Washington, D.C. Among other results, they reported that 16% of participants dropped out because of injury.

In public and in court, CrossFit has alleged that the injury statistic is false. CrossFit also claims that the journal's publisher, the National Strength and Conditioning Association (NSCA) of Colorado Springs, Colorado—which is a competitor in the fitness business—intentionally skewed the study to damage CrossFit. NSCA in turn has countersued, accusing CrossFit executives of defamation. Amid the legal crossfire, the journal first corrected the paper to reduce the number of injuries associated with CrossFit, then retracted it last year, citing changes to a study protocol that were not first approved by a university review board.

CrossFit suspects the paper's reviewers and editors worked to play up injuries associated with its regimen, and it has asked both federal and state judges to force the publisher to unmask the reviewers. In 2014, a federal judge refused that request. But last month, Judge Joel Wohlfeil of the San Diego Superior Court in California, who is overseeing NSCA's defamation suit against CrossFit, ordered the association to provide the names.