L Land certificates, as documentary evidence of land ownership, are issued through the land registration mechanism in accordance with government regulation number 24 of 1997 and its implementing regulations. however, in practice, land certificates have been issued over marine waters in connection with the coastal fence project in kronjo village, tangerang regency, where such issuance did not follow the statutory land registration mechanism. the issues examined are, first, whether the issuance of land certificates for the coastal fence in kronjo village, tangerang regency, complies with the prevailing laws and regulations. second, what legal remedies may be pursued by the residents of kronjo village to annul land certificates that have already been issued by the tangerang regency land office. to address these issues, this research employs a normative juridical research method with a descriptive-analytical approach, relying primarily on secondary data, and drawing conclusions through deductive reasoning. the findings indicate that the issuance of land certificates in the marine waters of kronjo village, tangerang regency, is legally defective in terms of administrative law, as it does not conform to government regulation number 24 of 1997, government regulation number 18 of 2021, and regulation of the minister of agrarian affairs/head of the national land agency number 16 of 2021. as a consequence of such administrative defects, the land certificates concerned may be annulled, the rights attached thereto are extinguished by operation of law, and any legal acts carried out on the basis of those certificates are likewise null and void by operation of law.