Japan should enact a law banning hate speech to protect the nation's ethnic minorities, according to a United Nations expert who said such a change would not impact freedom of speech.

"The international law makes it quite clear that in certain circumstances (hate speech) must be prohibited," Rita Izsak, a U.N. special rapporteur on minority issues, said at a symposium held in Tokyo late last month.

Izsak claimed restricting hate speech with penal sanctions can be justified as long as it is legitimate and such curbs are necessary and proportionate to protect the self-esteem of targeted groups.