In the midst of increasingly complex security challenges in the Indo-Pacific region, upholding the rules-based order (RBO) has emerged as the key objective for many states, most notably Japan. While previous research has mainly examined how states uphold the RBO in tandem with strengthening the rule of law (ROL), this article disentangles the relative importance of both objectives and shows that the ROL has become the far more critical norm for Japan. Using a qualitative content analysis and a neoclassical realist perspective, we make three key findings: first, the relative importance of ROL has increased significantly in Japan, especially since 2016. Second, however, Japan’s focus on ROL-based foreign policy dates back to the early 2000s and is therefore not a recent phenomenon. And third, the ROL has been particularly viable in terms of engaging with states in the region using international law as a common denominator.