Du Huan (fl. c.760), for those who are not familiar with his rather remarkable history, was a Chinese soldier who was born in the Tang capital, Chang'an (which stood on the site of modern Xi'an), and was captured at the Battle of Talas. This battle, which is notable as the first major encounter between two of the strongest powers in the world at that time, was fought to the east of Transoxiana – what is now in Northern Kyrgyzstan or Southern Kazakhstan – in 751 between outlying forces of the Abbasid Caliphate and the Tang empire.

Du Huan and other Chinese prisoners captured in the battle were taken back to the Abbasid capital, Kufa, which was located south of Baghdad in what is now Iraq. Du Huan appears not to have been actually held captive but to have been free to travel fairly widely. Unfortunately, nothing regarding the precise timeline of his years in the west has survived; all we know is that he was able to return to China by sea eleven years later, in 762, using the maritime trade route that was just coming into existence in those years between Siraf, in the Persian Gulf, and Guangzhou (Canton) in southern China.

The main reason why we know comparatively little about Du Huan and his voyages is that the Jingxingji, or Travel Record – the book he wrote on his return to China that described them – has been lost. Only a few extracts, totalling about 1,500 characters, have survived; these were incorporated into Scrolls 191 and 193, passages devoted to 'Border Defence' that formed part of the 200-scroll 通典 (Tongdian, or Encyclopaedic History of Institutions), a work compiled c.801 by a relative, Du You (735-812). The Tongdian was submitted to the imperial court, and so entered the Tang state library system to be preserved in its entirely. Sadly, there is no indication that the Travel Record circulated outside Du Huan's family, which probably explains why it has not survived.

This is especially unfortunate in that Du Huan led a remarkable life and offers a lot of precise information in the extracts of his work that have survived, much of which, where checkable, appears to be pretty accurate. He genuinely does seem to have travelled widely and reported back in detail on the places he had seen. And, while Schottenhammer cautions that "it is unlikely that Du Huan visited all of the countries and regions he wrote about personally" and that "some information was probably based on hearsay, as he describes various areas only briefly and superficially," he tends to preface such passages with the comment "It is also said..." This means there is hope we can distinguish between the things that he actually saw in person, and the stories he records that were related to him by other informants – such as one passage that describes a tree on a rock in an ocean, which bears fruit in the form of tiny children about 6 inches [15cm] long "which do not speak but all can laugh and move their hands and feet."

Now, with all this said, I need next to admit that I've encountered some other problems in attempting to address your question. Unfortunately, I don't read Chinese, and in the midst of the current pandemic I also have no access to research libraries or to the Tongdian in any form in full, so I'm reliant on the works I have here at home in my own library. This is especially unfortunate in that Du Huan's writings appear in variant forms in the secondary works I've actually consulted for you. What I'll do, then, is set out my findings and the alternative interpretations available as precisely as I can. That way, we will at least take some steps towards a full solution – but that solution, regrettably, is going to need to come from a Chinese speaker with access to the Tongdian. I'll add that the best starting place for someone with the correct linguistic skills appears to be the critical commentary on this work edited by 王文錦 (Wang Wenjin) and published in Beijing by Zhonghua in 1988.

Anyway: two particular excerpts concern us; it seems they appear consecutively in the Tongdian. The first describes one of the countries that Du Huan visited, and the second the competing systems of law that you have referenced. However, the three variant translations I have to hand are pretty different, to the point I wouldn't feel confident in following one translation, or ordering, over the others without more opportunity to research.

Let's begin with the translation offered by the German ethnographer Wolbert Smidt. His work on the subject is the most focused, the most scholarly and the most precise available to me, and so, while we have to note that he uses it to prove some specific assertions about the places that Da Huan actually visited, I think we need to privilege it, which is why I begin with it here:

We also went to Molin, Southwest of Yangsaluo. One reaches this country after having crossed the great desert and having travelled 2,000 Li. The people there are black, their customs rough. There is little rice and cereals and there is no grass and trees. The horses are fed with dried fish, the people eat XX [word not identified] and also Persian dates. Subtropical diseases [Malaria] are widespread. After crossing the inland there is a mountainous country, there are a lot of confessions.

The followers of the confession of the "Dashi" [the Arabs – thus, Islam] have a means to denote the degrees of family relations, but it is degenerated and they don't bother about it. They don't eat the meat of pigs, dogs, donkeys and horses, they don't respect neither the king of the country, neither their parents, they don't believe in supernatural powers, they perform sacrifice to heaven and to no one else. According their customs every seventh day is a holiday, on which no trade and no cash transactions are done, whereas when they drink alcohol, they are behaving in a ridiculous and undisciplined way during the whole day. Within [a missing term here in Smidt seems to be Daqin, the Chinese word that can mean either "Rome" or "Syria" – though Du Huan also uses "Fulin" to mean Byzantine Empire and "Shan" to mean "Syria" – but he simply has "[East Roman] confession". At any rate, what is actually meant here is "Christianity"] the medical doctors know diarrhoea – or they recognise it already before the outbreak of the disease, or they open the brain and insects come out.

Next we have the translation of Li Anshan, in his A History of Overseas Chinese in Africa. This suggests that the passage you are interested in follows directly on from the section on the Molin state, or kingdom, or country (the same Chinese word, 'guo', can be translated to mean any of these terms):

We then visited the Mo-lin Kingdom. It was to the southwest of the Jiu Sa Luo Kingdom. We crossed a large river, walked two thousand miles and reached the kingdom. People there were black, rude, and uncivilized. There were few grains, no grass or trees. Horses ate dry fish. People ate Niao Mang, which is Asian Dates. There were a lot of plagues. The kingdom was on a land route to many other kingdoms. There was one country, governed by several laws: Dashi Law, Daqing Law, and Xunxun Law. Xunxun Law was the harshest law among all foreign laws. Talking was forbidden during meals. Under Dashi Law, people punished their own family and children, even for minor faults. This was so that they themselves would not be blamed for others' crimes. People there did not eat pig, dog, donkey, or horse meat. They did not revere or worship their kings or parents. They believed in deities and ghosts. Its custom was to set aside one holiday for every seven days. On holidays, sales and banking were banned; people drank alcohol and played all day.

Note, here, that neither Smidt nor Li Anshan state explicitly that the "one country 'governed by several laws'" that you are interested in is necessarily Molin, and in fact Smidt's translation implies that the two are distinct places, separated by mountains.

This problem becomes significant when we move on to the third translation available to me, by Wan Lei. This version separates the two passages and inserts a sub-heading at this point, which appears to be the translator's own interpretation of what follows. As such it definitely seems to suggest we cannot assume the passage on laws necessarily refers to Molin – but while Smidt seems to suggest the land of three laws is a distinct place, Wan Lei instead implies the three laws are common to many of the places he visited. We'd need to consult the Tongjian in the original to be certain which of these approaches is the more nearly accurate.