The distinction between qath‘iy (definitive) and zhanniy (probabilistic) has long been a fundamental aspect of Islamic legal theory, particularly in determining the authority, certainty, and interpretive scope of Islamic legal texts. In the context of modern state governance, this distinction raises significant questions regarding the relationship between Islamic legal principles, constitutional interpretation, and the evolving demands of contemporary political and legal institutions. This study aims to examine the conceptual relevance of qath‘iy and zhanniy as a framework for Islamic constitutional interpretation and to analyze their implications for modern state governance. Employing a qualitative approach through normative legal research, this study utilizes a conceptual and analytical method by examining classical Islamic jurisprudence, principles of uṣūl al-fiqh, and contemporary constitutional theory. The findings indicate that the distinction between qath‘iy and zhanniy provides an epistemological foundation for differentiating between definitive normative principles and interpretive provisions that allow contextual reasoning and legal development. The study further demonstrates that qath‘iy principles may serve as normative foundations for constitutional values, while zhanniy provisions provide interpretive flexibility in responding to social transformation, institutional development, and changing governance needs. This distinction, however, requires careful consideration of both textual certainty (thubūt) and semantic certainty (dalālah), as well as the objectives of Islamic law (maqāṣid al-sharī‘ah). The study concludes that integrating the qath‘iy–zhanniy framework into Islamic constitutional interpretation can contribute to a balanced approach to modern state governance by maintaining normative consistency while accommodating constitutional adaptability, justice, and public welfare.