Cost/Benefit of Illegal Immigrants

I finally found a reputable study on net cost, from the Wall Street Journal:
"The President's Council of Economic Advisers added up all these costs and benefits, updating the procedures used by the National Academy of Sciences, and concluded that the value of non-citizen immigrants to the overall economy is a net positive $30 billion a year."

It makes sense to me that the value of US products that illegal immigrants purchase exceeds the value of free US school/medical services they get. Of course this study only examines cost in dollars. There was no consideration of natural resource or infrastructure usage. Also it should be noted that $30 billion is not a large number in terms of percentages of illegal immigrant population, or percentage of US GDP. However, I am convinced that the only remaining valid arguments for tightened immigration control are:

1) rule of law
2) security
3) language/culture preservation
4) possible depressed job/wage market for US citizens