The argument against the Strangers Into Citizens campaign - that it is wrong to reward illegal behaviour - is powerful but flawed. There would have been no peace in Northern Ireland without the release of convicted terrorists, no votes for women without the Suffragettes, no Magna Carta without the nobles' revolt. In modern times, the Poll Tax was repealed after riots in Trafalgar Square, the right to roam was enshrined in law after the Kinder Scout Trespass and the Conservative Party promises to overturn a ban on hunting that is openly flouted around the country.
Giving an amnesty to illegal workers is no different in principle to releasing paramilitaries in Ulster. You cannot hope to solve a problem unless you first acknowledge its realities.