ANALISIS PENERAPAN ASAS ITIKAD BAIK DALAM PENANDATANGANAN AKTA VAN DADING HASIL MEDIASI PERKARA PERDATA NOMOR 137/Pdt.G/2024/PN.Yyk (STUDI SENGKETA KASULTANAN YOGYAKARTA DAN PT KAI PERSERO DALAM GUGATAN PERBUATAN MELAWAN HUKUM)NIM.: 21103040195Fitrotul MufidahauthorThe land dispute between the Sultanate of Yogyakarta and PT KAI (Persero) in Case Number 137/Pdt.G/2024/PN.Yyk originates from an overlap in the status of 297,192 m² of land at the Tugu Station yard, which is legally classified as Sultanate Land (Sultan Ground) but has been treated as a fixed asset and/or State Property (Barang Milik Negara/BMN) of PT KAI. This study aims to analyse the juridical and structural reasons underlying the reluctance of the Ministry of State- Owned Enterprises, the Yogyakarta City Land Office (BPN), the Ministry of Finance, and the Ministry of Transportation to sign the van dading (settlement deed), and to assess whether such a stance may be regarded as a form of bad faith in mediation. This field research employs a empirical-legal approach with a descriptiveanalytical character, grounded in normative legal analysis of the Indonesian Civil Code, Supreme Court Regulation (PERMA) Number 1 of 2016, the BMN management regime (Government Regulation Number 27 of 2014, Minister of Finance Regulation 207/PMK.06/2021), Minister of Agrarian Affairs/Head of BPN Regulation Number 21 of 2020, Minister of SOEs Regulation Number 2 of 2010, and the special autonomy regulations of the Special Region of Yogyakarta. Data were collected through interviews with the mediation judge, a member of the judicial panel, and officials of BPN, courtroom observation, examination of the settlement deed and judgment, and literature review, and were analysed qualitatively using the Doctrine of Good Faith and the Theory of Legal Certainty The findings demonstrate that the principle of good faith is strongly reflected in the conduct of the Sultanate and PT KAI, who actively engaged in negotiation, signed the settlement deed, and followed up by initiating the derecognition of the asset through the General Meeting of Shareholder.. By contrast, the stance of the BMN-related institutions, which accepted the substance of the agreement but declined to sign the deed, was predominantly driven by normative prohibitions on settling disputes involving BMN, limited mandates of mid-level officials, and fiscal prudence. Accordingly, at the stages of mediation and the ratification of the settlement deed, this attitude cannot yet be unequivocally characterised as bad faith, provided that the administrative obligations set out in the van dading are genuinely implemented. Nevertheless, the configuration of “agreement without signature” risks undermining legal certainty if it is later invoked as a basis for evading enforcement of the judgment, and it reveals a regulatory gap in PERMA Number 1 of 2016 concerning the criteria for assessing good faith on the part of BMN-managing institutions within court-annexed mediation.340 Ilmu Hukum2026-07-30UIN SUNAN KALIJAGA YOGYAKARTA;FAKULTAS SYARI’AH DAN HUKUMThesis