I want to ask a master of law or demography, what are the laws and regulations about population migration in ancient China? Or can you look at the articles of those scholars in this field?

The quantity and quality of population were the basis of China's ancient social, economic and military strength, so the rulers of past dynasties encouraged the population to multiply and improve its quality. For example, while encouraging people to have more children, the Yuan Dynasty also set up primary technical training schools. Influenced by the employment thought of "emphasizing agriculture over industry and commerce", the employment structure of the population is mainly agriculture. The population expansion has caused the contradiction between man and land. All previous dynasties attached great importance to alleviating the contradiction between man and land and issued a series of farmland policies. For example, the Northern Wei Dynasty implemented the equal land system. Due to the vast territory of China, there are huge differences in the proportion of people and land in different regions. Encouraging immigrants has become another measure to alleviate the contradiction between man and land. Immigration has not only become an important way to solve the problem of population-land ratio, but also promoted the coordinated development of regional economy.

You can have a look at China Ancient Population Thought and Policy, which was edited by Mi and published by China Social Sciences Press.