Tujuan penelitian ini untuk mengetahui inkonsistensi ratio decidendi dalam putusan hakim dalam perkara perdata terkait standar legalitas ganti kelamin melalui pengadilan dan kepastian hukum bagi individu yang terlibat dalam proses tersebut dan syarat dan standar legalitas ganti kelamin melalui pengadilan. Metode penelitian yang digunakan adalah penelitian hukum Normatif dengan pendekatan perundang-undangan (statue approach), pendekatan kasus (case approach) dan pendekatan anatomi tubuh pada fisiologi, menggunakan bahan hukum penelitian yaitu bahan hukum primer, sekunder dan tersier. Teknik pengumpulan data dari penelitian ini adalah studi kepustakaan untuk mendukung
penelitian ini. Setelah dilakukan pengumpulan data maka hasil penelitian tersebut diolah dan di analisis secara deskriptif. Hasil Penelitian yang telah dilakukan menunjukkan bahwa inkonsistensi ratio decidendi dalam perkara perdata penggantian kelamin di pengadilan disebabkan oleh perbedaan penafsiran terhadap Undang-Undang Administrasi Kependudukan, asas kepastian dan kemanfaatan hukum, serta pertimbangan medis dan agama. Hal ini menimbulkan ketidakpastian hukum bagi individu yang permohonannya ditolak, berdampak pada kesulitan dalam dokumen kependudukan (KTP, paspor, KK), hambatan hak sipil (pernikahan, waris), serta diskriminasi sosial dan administratif akibat perbedaan antara identitas hukum dan sosial. Meski belum diatur secara eksplisit dalam peraturan perundang-undangan, praktik hukum
menunjukkan adanya empat syarat utama dalam permohonan ganti kelamin di pengadilan, pertama, adanya kondisi medis, kedua, belum melakukan operasi sebelum ada putusan, ketiga, telah mencoba upaya medis lain, dan memiliki bukti medis yang kuat. Legalitas penggantian kelamin di pengadilan didasarkan pada dua komponen: surat permohonan dan bukti medis, yang meliputi hasil pemeriksaan genetik/kromosom, diagnosa dokter spesialis, hasil pemeriksaan psikologis, dan surat keterangan operasi (jika sudah dilakukan).
The purpose of this study is to determine the inconsistency of ratio decidendi in judges' decisions in civil cases related to the legal standards of sex change through the courts and legal certainty for individuals involved in the process and the requirements and standards for the legality of sex change through the courts. The research method used is Normative legal research with a statute approach,
a case approach and an anatomical approach to physiology, using legal research materials, namely primary, secondary and tertiary legal materials. The data collection technique for this study is a literature study to support this research. After data collection, the results of the study were processed and analyzed descriptively. The results of the study that have been conducted show that the inconsistency
of the ratio decidendi in civil cases of sex reassignment in court is caused by differences in interpretation of the Population Administration Law, the principles of legal certainty and benefit, and medical and religious considerations. This creates legal uncertainty for individuals whose applications are rejected, resulting in difficulties in population documents (KTP, passport, KK), obstacles to civil rights (marriage, inheritance), and social and administrative discrimination due to differences between legal and social identities. Although not explicitly regulated in laws and regulations, legal practice shows that there are four main requirements
for applications for sex reassignment in court, first, the existence of a medical condition, second, not having had surgery before a decision is made, third, having tried other medical efforts, and having strong medical evidence. The legality of sex reassignment in court is based on two components: a letter of application and medical evidence, which includes the results of a genetic/chromosome examination, a specialist doctor's diagnosis, the results of a psychological examination, and a certificate of surgery (if it has been performed).