A Mississippi federal trial court judge ruled yesterday that a public high school violated a lesbian student’s First Amendment rights by preventing her from bringing her girlfriend to the prom. In a case that has been drawing national attention, the Itawamba County school board canceled the prom rather than allow high school senior Constance McMillen to bring another female student as her date. U.S. District Court Judge Glenn Davidson determined that the ban constituted viewpoint-based discrimination that violated McMillen’s right to free expression.

Mississippi doesn’t ban discrimination based on sexual orientation, and the U.S. Supreme Court has not recognized it as a form of gender bias, so there goes the obvious equal-protection argument. Invoking the First Amendment is a creative move. But is it logical? I could understand it better if McMillen were a transgender student defending her right to cross-dress. Dating seems more like conduct than speech. Being gay is not exactly a viewpoint.

Looking at the big picture, some important protections for women and sexual minorities actually depend on keeping clear definitional boundaries between speech and action. In pornography, violent and medically dangerous acts are sheltered under the umbrella of “free speech” (wrongly, in my opinion) because a camera is rolling, avoiding the restrictions that OSHA would impose on any other hazardous occupation. It’s rotten to get kicked out of your prom, but bullying is a more pervasive problem that GLBT teens face day-to-day. The first national study of cyberbullying of GLBT youth, released last week by Iowa State University, found that more than half of those youth and their self-identified straight allies had experienced online harassment during a one-month period.

In this environment, well-meaning judges should think twice about extending students’ free expression rights beyond their common-sense limits.