If the people of a country chose to live according to Catholic values then what's the issue? If they elect a government that will express this in its policies, then what's the issue? Matters of border control are a matter for the prudential judgement of a nation's secular government and, in a democracy, they will have the support of the electorate. These are not decisions for the Church, although it is appropriate for the Church to put forward a view and to seek to influence the faithful. Multiculturalism is not a doctrine of the Catholic Church and is proving to be a demonstrable failure in many European nations.