Human Rights Watch is urging Japan to drop its requirement that transgender people be sterilised to have their gender changed on official documents.
A 2004 law states people wishing to register a gender change must have their original reproductive organs removed and have a body that "appears to have parts that resemble the genital organs" of the gender they want to register.
The Supreme Court in January rejected an appeal by a transgender man who wanted legal recognition without undergoing surgery.
Human Rights Watch said the compulsory sterilisation requirement is abusive and outdated.
A report the international rights group released Wednesday said requiring invasive and irreversible medical procedures violates the rights of transgender people who want their gender identity legally recognised.