The Conservatives have been promising since they came to power in the Coalition Government six years ago to bring net migration down from outside the EU down to tens of thousands. They have signally failed to do that. Whatever the reasons for failing in this goal, this cannot be because the UK government does not control its own borders. It does. Leaving the EU won't stop non EU nationals coming into the country. It may reduce the number of EU nationals, but it doesn't look hard for someone without an EU passport to settle in Britain, so would it really make much of a difference?
The Brexit camp accept that immigration is necessary - they want to control it, not to stop it. But on what basis? They cite the Australian "points system" which ensures that people are only allowed in if they have skills the country needs.
My first thought was "I bet the native born Australians (the group of indigenous people we disparagingly refer to as 'aborigines') wish they had thought of such a scheme when Britain started dumping its convicts on them in the 19th century.
My second thought was "oh, so we want to make sure that only skilled people come into the country, so that we can keep all of the unskilled, low paid jobs for the native population". (I'm sorry I am still thinking of Australia here!) Do our young people really have no higher aspirations than to be assured of a job sweeping the streets or cleaning cars when they leave school?