According to....
http://en.wikipedia.org/wiki/Timeline_of_the_history_of_the_Falkland_Islands
1816: The United Provinces of the Río de la Plata, later called Argentina, claimed independence from Spain.
1825: The United Kingdom recognised Argentina's independence from Spain.
1850: Britain and Argentina sign the “Convention between Great Britain and the Argentine Confederation, for the Settlement of existing Differences and the re-establishment of Friendship”. Several historians (Argentine, British and Latin American) consider this has a negative impact upon Argentina's modern sovereignty claim.
1884: Argentina request that the sovereignty dispute is submitted to independent arbitration, Britain refuses. The first mention of the Falkland Islands by Argentina for 34 years.
1888: Argentina lodges a diplomatic protest with the UK, the matter is not raised again with the UK until 1941.
1941: The issue of the sovereignty of the Falkland Islands is raised by Argentina in a Message to Congress. This is the first time since the signing of the Convention of Settlement in 1850.
1945: Formation of the United Nations, Argentina states its claim to the islands in its opening address.
1946: Britain includes the Falkland Islands among the non-autonomous territories subject to its administration, under Chapter XI of the UN charter.
1947: Britain first offers to take the sovereignty dispute over the Dependencies to the ICJ. Argentina does not accept.
1948: Britain again offers to take the sovereignty dispute over the Dependencies to the ICJ. Argentina declines.
1955: Britain unilaterally refers the sovereignty dispute over the Dependencies to the ICJ. Argentina indicates that it will not accept any judgement.
Hence, any Argentine representation to the UN has to be taken into account of these historical facts, as Argentina has for almost 150 years refused any arbitration as to the actual ownership of the disputed landmass, (see 1950).
So, as to attribute ownership to Argentina as the OP states, then this is vvvvvv doubtful, IMO, but is due to the stated requests in 1950 (by Argentina), the basis of Argentina's claim is neutered by the position that "Argentina indicates that it will not accept any judgement." of ICJ