In the United States, this question takes the form of analyzing the distinction between ‘legal’ and ‘illegal’ immigration. It is a question of law, and of knowing and deliberate violation of the law.
Legal immigrants are, by definition, welcome in the United States. They contribute to the economy and pay their prescribed taxes. They can eventually become full citizens.
Illegal immigrants are criminals, because they have understood the rules beforehand, and have chosen to break those rules. They pay fewer taxes and are therefore not fully supporting the system from which they draw significant social benefits.
The political controversies emerge when people use the word ‘immigrant’ without clearly stating whether they are referring to legal or illegal immigrants.
The example of California is instructive. In 1994, the state had between 1.3 and 2 million illegal immigrants. The exact number is, of course, difficult to determine, because illegal immigrants are constantly working to conceal the fact that they have violated the law.
In that year, California’s voters approved Proposition 187, which was designed to ensure that legal immigrants received social benefits, and to ensure that illegal immigrants did not take those benefits from the legal immigrants.
Because 1994 was a statewide election year, the voting on Proposition 187 was linked with the voting on candidates for various statewide offices. An editor for the University of Michigan’s Michigan Law Review writes:
In 1994, Governor Pete Wilson of California pulled off an amazing come-from-behind victory by tethering himself with titanium cords to Proposition 187, which prohibited illegal aliens from collecting public services. Wilson went from a catastrophic 15 percent job-approval rating to a landslide victory. Suddenly he was being touted as presidential material.
Unrelated the California’s Proposition 187, but related to the topic of immigration, journalist Martin Wolf, writing for the Financial Times, reports that
The share of immigrants in populations has jumped sharply. It is hard to argue that this has brought large economic, social and cultural benefits to the mass of the population.
Note that immigration itself is not harmful to national economies, but illegal immigration does serious damage. Legal immigration has beneficial effects, but illegal immigration is a major problem facing various world governments in the early twenty-first century.