Oh, yes it is... what? Your reading comprehension need improvements ...
If you want to bring time elapsed into this, it still render Chinese claim invalid because the 1954 Geneva Conference effectively grant South Viet Nam authority and custodial rights BEFORE China presented her claim.
Funny wasn't it!? It was the victory of Dien Bien Phu in 1954 by the North Vietnam so that came the 1954 Geneva Conference and yet "
These agreements separated Vietnam into two zones, a northern zone to be governed by the Viet Minh, and a southern zone to be governed by the State of Vietnam, then headed by former emperor Bảo Đại." Bao Dai, was then the puppet of France. Therefore, according to NIDS Security Reports that "
... with the French withdrawal in the mid-1950s, South Vietnam began claiming territorial rights over the Paracel Islands and the Spratly Islands, and put the western part of the Paracels and a part of the Spratlys under its effective control. Meanwhile, China took over the eastern part of the Paracels in 1956."
That was where you were wrong Gambit for China already made herself presence at Paracel Islands in 1956.
Here is where you and the other Chinese boys are wrong...
In principle, the 12-mile territorial limit should be respected by everyone and that was what Phạm Văn Đồng conceded to in his 1958 response to China. But there were contestant claims to the islands
BEFORE the Chinese declaration and NVN's response. That mean while the contestant claims do not negate the general idea that someone's territorial waters should not be violated, the contestant claims do put in doubt the validity of the islands' sovereignty belonging to China.
You are wrong even further into this argument when saying that "
there were contestant claims to the islands BEFORE the Chinese declaration and NVN's response." Why? Because those islands were not belong to Vietnam either due to many contestant claims. Apparently, China is one of many contestant claims, right!?
So if NVN did not, or rather could not, concede something to someone else what it never had in possession in the first place, that response is exactly what it is: A gesture of courtesy between nation-states.
Again, this childish analogy repeats its ignorance. PM Pham Van Dong, a Vietnamese, knew real well that those islands (Paracel & Spratly) are parts of Vietnam as a whole, although Vietnam was in the Civil war and yet he signed anyway to agree with what China's claims. You can make excuse for not having the possession of the islands in the first place, but it also shown how cruel NVN toward SVN during the Civil War. What is belong to the South VN's brothers can be used for diplomatic political's benefits.
SAD, but too bad - like the old saying:
What is written binds the writer.
If your property is being claimed by someone else, as a third party, my opinion regarding sovereignty of that property has no legal value, especially when your claim to that property is much stronger than the second party's claim. I could make a general statement that property rights should be respected...blah...blah...blah...and that still would not have any effects on the contest.
What if that someone else eventually stole my property with the help of the third party? Do you consider someone else and the third party are thieves to me then?
An equally appropriate analogy is that of a divorce, and I have been through one. In a marriage, community properties are held in legal 'limbo' until both parties agreed upon whose authority and custodial rights can be conferred upon which item. If there is an external contestant claim on an item, in principle, the item's sovereignty still belongs to the couple in a marriage partnership. Not the husband's. Not the wife's. But the couple's. Both can unite to challenge said contestant claim to that item and the court would recognize their unity despite the fact that the court know they are going through a divorce. Both MUST unite because if the item is lost to the challenger, no one in this partnership benefits, especially if the item is of value from long time possession and development. Only after the divorce is finalized and the list of community properties itemized as belonging to who could either party separate each other's authority and custodial rights from the items and do with them as each see fit.
I am sorry to hear about your divorce but you don't have to bring your personal matter into this argument. However, the more analogy you want to make just turn out to be against you dearly ...
As you said: "
... in principle, the item's sovereignty still belongs to the couple in a marriage partnership. Not the husband's. Not the wife's. But the couple's. " Then how could you to keep saying that NVN did not have sovereignty over the item - which is the two archipelagos?
Both analogies are eminently applicable in this dispute. North Viet Nam never had authority and custodial rights over the islands, therefore, Phạm Văn Đồng conceded nothing to China except acknowledgement of respect to a general principle that everyone has to anyway. Both Vietnams were in a civil war so any diplomatic treaties produced by either sides are applicable only to the items that are directly under its controls. South Viet Nam could not give the US access to mainland China, right? Then could North Viet Nam give China access rights to US mainland? See how absurd those questions are?
If you said that North Viet Nam never had authority and custodial rights over the islands, then South Vietnam was equally had no authority and custodial rights over the islands either. Why? Because there was a Civil War in Vietnam as a divorce from your analogy.
About your absurd questions that I can help you clear your mind:
1. South Viet Nam could not give the US access to mainland China, right? - US doesn't need South Vietnam to give her access to mainland China.
2. Then could North Viet Nam give China access rights to US mainland? China doesn't need North Vietnam to give her access to US mainland either.
China and US have each other's embassy in its own country.
France was colonial master in Indochina and asserted authority and custodial rights to the islands. The 1954 Geneva Conference assigned same authority and custodial rights to South Viet Nam as a temporary measure. If a husband and wife want a divorce, someone still has to live in the house to maintain it, to protect it from vandals, to repair damages from the weather, to protect other properties that the house shelters, and so on...That temporary authority and custodial rights does not give North Viet Nam the right to agree to any contestant claim by China or any other aspiring thief.
France was nobody after 1954 Geneva Conference and Vietnam was in a divorce procedure. They both lived in the same house, but in different rooms. Those islands were like the sheds outside in the back yard. During the divorce procedure, the husband with the help from the next door neighbor overtook the whole house and everything and kicked the wife out by force. What do you call to that?
Get your history straight, not crooked from the Chinese view. By the time of the 1954 Geneva Conference, Bảo Đại no longer mattered but South Viet Nam was governed by Ngô Đình Diệm.
You need to get your history straight my dear Gambit!
BAO DAI - Emperor of Vietnam
Reign 8 January 1926 – 25 August 1945 (19 years, 229 days)
Predecessor Khai Dinh
Heir-apparent Bao Long
Head of State of South Vietnam
Reign 13 June 1949 – 30 April 1955
versus
NGO DINH DIEM
In office
26 October 1955 – 2 November 1963
So you tell me that by the time of the 1954 Geneva Conference, Bảo Đại no longer mattered but South Viet Nam was governed by Ngô Đình Diệm. How twisted you are, huh? BTW, the Geneva Conference took place during (April 26 – July 20, 1954). Still, you try to deny the fact that France conceded whatever territory she controlled at that time to the best available authority figure she believed to be most capable of assuming authority, Bao Dai - her colonial puppet, which was South Viet Nam!
Then the same question can be applied to China as well. If anything, successful resistance to contestant claims, especially if said resistance involved military means, claim of sovereignty are reinforced.
Well, you can fight to claim what is yours involved military means and that what happened in 1956. China got two big islands in Parcel archipelago and Vietnam got other smaller ones. Each one got some islands of sovereignty that they have been controlling since. Therefore, you can't say nothing about it.
This is absurd and it shows why the Chinese arguments should be laughed at. What has China done to the islands as far as the same EEZ goes? Nothing except making a claim. Your argument is inherently illogical. China's claim is absolute and immune from challenging evidences while contestant claims must be subjected to microscopic legal scrutiny.
Gambit, Gambit ...
Aren't you and the Vietnamese posters using the EEZ line as a reason to show that China violated the UNCLOS 1982?
If you want to have sovereignty over the islands then how do you explain this map:
What is the legality of a claim that shown in this picture and communist government of the unified Viet Nam have done to her presence on the islands?
Remember, as you said: "
there were contestant claims to the islands BEFORE the Chinese declaration and NVN's response."
however credits need to be deliver when its due, man, you got "some debating skills" 
