I agree. However, recent polls among rank and file Libertarians are showing a turnabout on the issue, especially after 9/11. The latest Libertarian argument against open immigration is based on the definition of private property. The US, being the private property of its citizens, has every right to prohibit trespassers.
"The libertarians however are even WORSE than Bush regarding the illegal immigrant problem."
This is true, but I think something needs to be mentioned. Until the last few years, the issue with illegal immigrants has had little to do with national security. Before 2001, people were less concerned with terrorists crossing the border. The arguments were almost exclusively about illegals being a drain on taxpayer resources.
To be fair to Libertarians, those who believe in open borders also agree with eliminating the government hand-outs which make crossing the border so enticing for layabouts. The situation we have now is akin to the government leaving out a free chocolate cake, being shocked that people want to eat it for nothing, and then as a solution, deciding to place armed guards and barbed wire around the chocolate cake. It simply makes more sense to take the chocolate cake away instead of paying even more to put a fence around it. That's basically the libertarian position, and I find it very easy to be sympathetic to that idea before 9/11.
On the other hand, I don't think there is some kind of constitutional problem with limiting immigration. If the government wants to do that, it has the constitutional authority to do so. I don't think anyone arguing the opposite is on firm ground.
From the Libeltarian site.
CRIMINAL INVADERS unite.
The benefits of open immigration
BY MICHAEL TANNER
America has always been a nation of immigrants. Thomas Jefferson emphasized this basic part of the American heritage, taking note of "the natural right which all men have of relinquishing the country in which birth or other accident may have thrown them, and seeking subsistence and happiness wheresoever they may be able, and hope to find them."
The Libertarian Party has long recognized the importance of allowing free and open immigration, understanding that this leads to a growing and more prosperous America. We condemn the xenophobic immigrant bashing that would build a wall around the United States. At the same time, we recognize that the right to enter the United States does not include the right to economic entitlements such as welfare. The freedom to immigrate is a freedom of opportunity, not a guarantee of a handout.
A policy of open immigration will advance the economic well-being of all Americans. All major recent studies of immigrants indicate that they have a high labor force participation, are entrepreneurial, and tend to have specialized skills that allow them to enter under-served markets. Although it is a common misconception that immigrants "take jobs away from native-born Americans," this does not appear to be true. In 1989, the U.S. Department of Labor reviewed nearly 100 studies on the relationship between immigration and unemployment and concluded that "neither U.S. workers nor most minority workers appear adversely affected by immigration."