The United Kingdom and Argentina both assert sovereignty over the Falkland Islands. The UK bases its position on its continuous administration of the islands since 1833 and the islanders' "right to self-determination as set out in the UN Charter". Argentina claims that, when it achieved independence in 1816, it acquired the Falklands from Spain. The incident of 1833 is particularly contentious; Argentina considers it proof of "Britain's usurpation" whereas the UK discounts it as a mere reassertion of its claim.