Money laundering is not just an illegal transaction, but a mechanism that allows criminals to disguise the proceeds of crime so that they can be used without suspicion. Therefore, the crime of money laundering is often closely related to predicate crimes, such as corruption, narcotics, fraud, and other crimes that are the source of funds for these illegal practices. The research method uses normative legal research, with the nature of analytical descriptive research, with the approach of legislation approach, concept approach, and case approach. Sources include primary, secondary and tertiary legal materials. The data collection technique is through library research. The data collection tool is document study (documentary research), then analyzed qualitatively. This legal construction has fulfilled the principle of legal certainty because it is formulated clearly and structured in the Money Laundering Law. Law enforcement officers should be more careful in proving the subjective and objective elements of the offense of Article 3 of the TPPU Law, so that criminal liability is not imposed on parties who do not fulfill the elements of actus reus and mens rea in their entirety. The panel of judges in deciding the case does not only adhere to formal interpretation, but also carefully considers the legal facts, as well as substantive justice and proportionality of the defendant's role, so that the decision truly reflects the balance between legal certainty, benefit, and justice.Keyword: Ratio Decidendi, Money Laundering, Crime, Fraud.Abstrak: Pencucian uang bukan sekadar transaksi ilegal, tetapi merupakan mekanisme yang memungkinkan pelaku kejahatan untuk menyamarkan hasil kejahatan agar dapat digunakan tanpa dicurigai. Oleh sebab itu, tindak pidana pencucian uang sering kali berkaitan erat dengan kejahatan asal (predicate crime), seperti korupsi, narkotika, penipuan, dan tindak pidana lainnya yang menjadi sumber dana bagi praktik ilegal tersebut. Metode Penelitian menggunakan penelitian hukum normatif, dengan sifat penelitian deskriptif analitis, dengan pendekatan yaitu pendekatan perundang-undangan, pendekatan konsep, dan pendekatan kasus. Sumber meliputi bahan hukum primer, sekunder dan tersier. Teknik pengumpulan data adalah dengan studi kepustakaan (library research). Alat pengumpulan data yaitu studi dokumen (documentary research), kemudian dianalisis secara kualitatif. Konstruksi hukum ini telah memenuhi prinsip kepastian hukum karena dirumuskan secara jelas, dan terstruktur dalam Undang-Undang Pencucian Uang. Seharusnya, aparat penegak hukum lebih teliti dalam membuktikan unsur-unsur subjektif dan objektif delik Pasal 3 UU TPPU, agar pertanggungjawaban pidana tidak dijatuhkan kepada pihak yang tidak memenuhi unsur actus reus dan mens rea secara utuh. Majelis hakim dalam memutus perkara tidak hanya berpegang pada penafsiran formil, tetapi juga mempertimbangkan fakta-fakta hukum secara teliti, serta keadilan substantif dan proporsionalitas peran terdakwa, agar putusan benar-benar mencerminkan keseimbangan antara kepastian hukum, kemanfaatan, dan keadilan.Kata kunci: Ratio Decidendi, Pencucian Uang, Kejahatan, Penipuan.