I have to admit that my thinking regarding the immigration issue has changed significantly over the past couple of years as I have spent more time reading and listening the to arguments on both sides. One of the major shifts occured when I began to look at and study the difference between types of law: malum in se and malum prohibitum.
Here’s a quick overview from Cafe Hayek:
A critical distinction in Anglo-American law is that between actions that are malum in se and actions that are malum prohibitum. Some actions are malum in se — wrong in themselves. Examples are murder, rape, theft, and fraud. These actions are now formally prohibited by legislation, but their wrongness — indeed, their very illegality — exists independently [emphasis added] of legislative prohibition. If, say, the Virginia legislature were to repeal its statutory prohibition on murder, murder would still be wrong and criminal in Virginia. Murderers would still be wrongdoers and criminals. If the State government refused to punish such criminals, people would do so privately.
Other actions are malum prohibitum — “wrong” merely because the government proclaims these actions to be wrong. One example is avoiding taxes. If Uncle Sam tomorrow abolishes the federal income tax, failure of Americans to send money to Washington would be neither wrong nor criminal, and persons who send no money to Washington would not be regarded by their neighbors and co-workers as despicable louts whose company should be avoided.
Immigration law is clearly a malum prohibitum type law, as such it is a-moral, meaning that if we removed all immigration law people coming here would not be considered immoral. Thus it follows that the “criminality” aspect of an immigrant not following the law is no different that a legal citizen breaking the speed limit.