Typical approaches are either to obtain a law degree through a U.S. law school (a graduate degree in the U.S.) or to obtain a law degree in your home country then pursue an L.L.M. through a U.S. law school. You don't need to be a citizen to go to school in the U.S., you just need a student visa, but you do need either an employment visa, permanent residency or citizenship to work in the U.S. as a lawyer.