In order to practice law in the United States, the one must take a bar exam.
Admission to the bar in the United States is the granting of permission by a particular court system to a lawyer to practice law in that system. Each US state and similar jurisdiction (e.g. territories under federal control) has its own court system and sets its own rules for bar admission (or privilege to practice law), which can lead to different admission standards among states. In most cases, a person who is “admitted” to the bar i s thereby a “member” of the particular bar.
One who is admitted, can then practice law in that jurisdiction.
A lawyer who is admitted in one state is not automatically allowed to practice in any other. Some states have reciprocal agreements that allow attorneys from other states to practice without sitting for another full bar exam; such agreements differ significantly among the states. It is important to contact the State in which you wish to practice for the requirements.
The Bar is the exam and also the group that governs Attorneys and provides regulations. Foreign lawyers may take the bar in cerain states if they fulfill all of the States requirements.
Foreign lawyers may work as in-house counsel in the United States, but they may not give advice on U.S. law unless it is based on the advice of a lawyer who is licensed in the appropriate jurisdiction.
Seven states already expressly permit foreign lawyers to work as in-house lawyers in the U.S. offices of their clients.