There is no universal answer that a U.S. practice licence is required for every TN case. State guidance separates classification from permission to practise, but the particular profession’s credentials and any additional requirements still need review. TN authorization should not be treated as permission to ignore licensing rules.
Ask two separate eligibility questions
First, determine whether you meet the TN category’s qualification requirements for the actual work. Second, ask the relevant regulator what is required to perform those activities in the intended jurisdiction. Some health-care work can also involve an immigration certification question.
This overview does not decide any profession-specific exception, supervised-practice arrangement or certificate requirement. Obtain the applicable answer using the precise duties and location before promising the employer that a licence can safely be addressed after work begins. Ask two separate questions and keep the answers apart, because they are decided by different authorities against different criteria.
The immigration question is whether the person and the proposed work meet the requirements of the classification, which turns on citizenship, a listed profession, the credential that profession requires, prearranged employment and a temporary purpose. The licensing question is whether the person may lawfully perform the regulated activity in the state concerned, which is decided by that state's board on its own rules. Neither answer determines the other.
It is possible to hold classification and be unable to practise, and it is possible to satisfy a board and not meet the immigration requirements. Where an employer or an adviser treats one as resolving the other, that is a misunderstanding worth correcting explicitly and in writing.