Kevin,
There is no such evidence of illegal immigration, only absence of evidence of legal status.

Of course there is.

I do not accept that. It is possible to prove you are legal, but absence of such proof is the only way to prove illegality.

As I asked, Keith, how would you go about proving your legal right to be here if challenged?

Birth Certificate. The problem is with folk born overseas and arrived as children without needing documentation then, but needing it now.

Jim,
"All countries have restrictions. "
Sez it all really - OK to turn ordinary people into criminals and deport them as long as it's sanctioned by Governments

What it sez is that no country allows unrestricted entry. It sez it is unfair to criticise this country for being the same as every other.