In all the debate about immigration, one thing often forgotten is that violation of national borders, i.e. illegal immigration, is in most countries an offense, and even more a criminal offense.
There are two types of offences: civil and criminal. The difference between them is that the former is a wrong perpetrated against a private, be it an individual, company, organization or party, so it is the victim's responsibility to seek redress for the wrong done to them. It usually, but not necessarily, concerns money.
The latter is a wrong perpetrated against society as a whole, and therefore criminal offences are prosecuted by the state or government, rather than by individuals.
Although there is overlapping in the sense that the same behaviours can give rise to both a criminal and a civil offence, and sometimes both kinds of legal actions can be pursued, this is an important distinction.
In Western countries generally, illegal immigration is a criminal offense.
Illegal immigrants violate the immigration laws and sovereignty of a country.
The fact that the punishment for illegal immigration is not enforced does not make it any less serious; it just makes its non-enforcers more irresponsible towards the society and the people they are supposed to protect against this crime.
In fact, giving amnesty to those who have violated immigration laws, as the UK Liberal Democrats had put in their manifesto before the 2010 General Election, would reward criminal behaviour and violate a fundamental principle of civil justice, i.e. that no-one should be allowed to profit from wrongdoing, a case of which is entering a country illegally.
In addition, it would obviously send the wrong message to all the would-be immigrants and act as a magnet for even more of them.