The 'international rules-based order' was established by the US at the end of WWII as the legal framework for rebuilding Europe after the war.

Honest question, what makes you think the US, China, or Russia need to abide by legal agreements made 80 years ago by people who aren't around anymore? Those three countries have since agreed amongst themselves that the 'international rules-based order' was a mistake, and nobody else has a big enough stick to do anything about it.