Originally Posted by Paul Markham

You missed out.

6. Dump them back where they came from.
7. Fine their employers, so much it funds more migration/border control officers.
8. Fine their landlords, so much it funds more migration/border control officers.

7 and 8 are a big problem. Look at the current fines for those who lure migrants and who gets fined.

How easy is it in the 21st Century to check if a person's documents are authentic? Very easy if the will is there to ask the police to check, of course, a database would make it very easy. But the words "knowingly" make it easy to ignore and stay safe.