In the interest of being accurate when commenting on a contentious issue, I should point out that my statement that these professions are only available to citizens in the US is not strictly true. The barriers to non-citizens wishing to enter law, medicine, dentistry, and so forth in the US are considerable, but they are still somewhat porous.

The barriers for citizens to enter law, medicine, dentistry are outrageous. The professional associations restrict supply on purpose so they can continue earning outsized salaries for skills that could easily be taught by the age of 22 for less than half the cost.