as you appear to be some alien from beyond the solar system on Earth: previously political boundaries were set on the outcome of armed conflicts Great Britain

as you appear to be some alien from beyond the solar system on Earth: previously political boundaries were set on the outcome of armed conflicts Great Britain won the last one against Spain, and gained Gibraltar as a result over 300 years ago these days we are slightly more enlightened and tend to mainly believe in self-determination the people living in Gibraltar wish to remain British giving them up to Spain against their wishes would be an act of imperialism (commonly frowned on in the 21st century)