公立学校における「親代わり」（in loco parentis）の法理

In the Mahanoy decision, Justice Alito, who wrote the concurring opinion, and Justice Thomas, who wrote the dissenting opinion, used the doctrine of "in loco parentis" to discuss the regulation of off-campus speech, but came to different conclusions. This paper will then review the historical background of the doctrine and the development of its precedents in the Supreme Court of the United States. Then, since Justices Alito and Thomas referred to the "in loco parentis" doctrine in their respective opinions in the Morse and Mahanoy decisions, in which the constitutionality of public school students' freedom of expression was challenged, the differences between the two Justices' interpretations of the "in loco parentis" doctrine will be discussed.