This article offers a comprehensive analysis of the legal dimensions governing market access and domestic regulation in tourism services under the framework of the World Trade Organization’s General Agreement on Trade in Services (GATS). It begins by outlining GATS’s obligations—Most-Favoured-Nation (MFN) treatment, transparency, market access, and national treatment—and examines their specific application to the tourism services sector. The discussion emphasizes that liberalization under GATS extends beyond mere market opening; it also aims to foster fair competition, enhance service quality, and align domestic regulatory practices with international standards. The study argues that while liberalization presents opportunities for attracting foreign investment and stimulating innovation, it must be complemented by robust mechanisms to protect consumer rights, uphold public interests, and ensure environmental sustainability. Moreover, the research underscores the necessity of establishing a level playing field for both domestic enterprises and foreign investors as a foundation for a balanced and competitive tourism market. By harmonizing international commitments with national regulatory frameworks, the tourism industry can achieve long-term sustainable growth, greater transparency, and deeper global integration. Ultimately, the findings suggest that aligning GATS principles with domestic tourism policies can enhance service quality, drive economic development, and strengthen international cooperation.