Read this: The Ming court appointed three Princes of Dharma (法王) and five Princes (王), and granted many other titles, such as Grand State Tutors (大國師) and State Tutors (國師), to the important schools of Tibetan Buddhism, including the Karma Kagyu, Sakya, and Gelug. According to Wang Jiawei and Nyima Gyaincain, leading officials of these organs were all appointed by the central government and were subject to the rule of law. Yet Van Praag describes the distinct and long-lasting Tibetan law code established by the Phagmodru ruler Tai Situ Changchub Gyaltsen as one of many reforms to revive old Imperial Tibetan traditions.

Who was the Phagmodru ruler?
What is the answer? (If it cannot be answered, return "unanswerable")
Tai Situ Changchub Gyaltsen