You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Sino-Tibetan_relations_during_the_Ming_dynasty

Context:
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.

Question:
Who was the Phagmodru ruler?

Tai Situ Changchub Gyaltsen