As with most "absolutes" in constitutional law, the Supreme Court's rule against regulating the content of speech is more a statement of a bias than an imperative. Among the qualifications the Court has made to the bias against content regulation, the most potentially sweeping involves government limitations on expression in restricted environments or special contexts. In the context of the military, prisons, government employment and the public schools, the first amendment presumption against content regulation becomes far less meaningful than in civil society generally. Indeed, the principle of freedom of speech is itself of doubtful applicability in these special environs.
C. T. Dienes & Annemargaret Connolly,
When Students Speak: Judicial Review In The Academic Marketplace,
Yale L. & Pol'y Rev.
Available at: https://digitalcommons.law.yale.edu/ylpr/vol7/iss2/3