The Constitution of Japan, enacted in 1946, protects freedom of expression in its article 21. If the legislature were to enact a ban on hate speech, then the constitutionality of that ban would become a critical issue. In light of the jurisprudence relating to freedom of expression established by the Supreme Court of Japan, it is highly likely that the Supreme Court would uphold the constitutionality of any such ban. However, constitutional academics have constructed an alternative freedom of expression jurisprudence mainly following that of the Supreme Court of United States. Under this alternative jurisprudence, it becomes much more difficult to uphold the constitutionality of any such ban, and this chapter considers whether and how such ban might be justified in Japan.