Constitutional FAQ Answer #45
Q45. "Can you tell me how did the states get the power to decide that people had to have so much studying, etc. in order to have a license, and if they do not have this license, then they are doing whatever they do illegally?
A. This is an inherent power of the state, a power the state has by virtue of being a state. In the Constitution, the powers not explicitly granted the federal government are left to the state. The ability to regulate professions would be one of those powers, or to regulate if you are able to drive. The issuance of a license to practice medicine, or law, or to be an exterminator, is one of the police powers of the state, as is the ability to issue fishing or driving licenses.