Which of the following is a requirement for interstate practice?

Licensing in multiple states is essential for interstate practice because each state has its own regulations regarding mental health professionals. When a practitioner wishes to provide services across state lines, they must obtain a valid license in each state where they are practicing. This requirement ensures that they adhere to the legal and ethical standards set forth by each state's licensing board, thus protecting the rights and safety of clients.

Practicing without any state regulation would be contrary to the legal requirements governing mental health practices, as it could lead to unlicensed practitioners offering services, which is not only illegal but also harmful to clients. Having clients in each state of practice does not automatically grant a practitioner the right to practice; it only demonstrates the necessity for compliance with each state's regulations. Lastly, compliance with only one state’s laws neglects the multi-jurisdictional nature of interstate practice, as mental health practitioners must be aware and compliant with the laws of all states in which they operate.