Here's an educated guess on why the Vietnamese PM wanted to meet with a foreign supreme court justice (this in itself is weird - he usually only meets foreign PMs/presidents for photo-ops).
The biggest LEGAL question in Vietnam at that time was the legality of Vietnam's claims to the Spratly and Paracel Islands, which are also claimed by China. Remember the whole business about China building artificial islands out of the reefs and atolls there? It was starting then and continuing now.
China argues, with some reason, that Vietnam relinquished its claim to the Spratlys and Paracels in 1958, when North Vietnamese PM Pham Van Dong acknowledged in writing Chinese suzerainty over the islands:
https:// commons.wikimedia.org/wiki/File:1958_diplomatic_note_from_phamvandong_to_zhouenlai.jpg
The North Vietnamese did this, reluctantly, because they owed China a large war debt from the Viet Minh's war against colonial France. Because the North Vietnamese didn't have enough cash or gold to pay the red Chinese, China wanted payment in opium/heroin from the Laotian poppy fields (which were controlled for many years by the Viet Minh and their Pathet Lao puppets). However, by 1958 the CIA had taken control of the Laotian poppy fields and the North Vietnamese had neither cash nor gold nor drugs with which to pay the Chinese. So, they paid by way of relinquishing claim to the Spratlys and Paracels.
In recent years, communist Vietnam (i.e. today's “Socialist Republic of Vietnam”) has made a creative argument to justify continued claims to islands and disavowing its 1958 communique. The justification is: In 1958, there were “two Vietnams” (North and South). And because the Spratlys and Paracels were claimed by South Vietnam all the way until its demise in 1975, and never reliquished by South Vietnam, therefore by virtue of the communist victory over South Vietnam in 1975, the islands now belong to the united “Socialist Republic of Vietnam”.
This is odd because, in every other circumstance, the Hanoi government has claimed that South Vietnam was an illegitimate junta, not a country, and that none of its diplomatic agreements carry any weight today.
I wonder whether Ginsburg was being consulted about how to explain this circuitous reasoning to the world, especially to the Chinese. Perhaps, the Vietnamese PM was asking Ginsburg for the USA's support of its rather curious reasoning about why its 1958 diplomatic decision should be voided. The cabal has many reasons for not wanting China to control the Spratlys and Paracels. These reasons have nothing to do with oil rights (the cover story) and not very much to do with shipping lanes. If you want to know why the Spratlys and Paracels are so valuable, you need to learn something about undersea bases, including those which exist from deep antiquity in Earth's history. That, my fellow anons, is a story for another day…