Whether you are using ChatGPT teaching exercises in the classroom, or forming boundaries on student usage in your course, or some combination of the two, the decision on how-- or how not-- to use ChatGPT in your class is a decision for you to make as the instructor. This decision should be made in conjunction with colleagues, department chairs, or program director, and with any program or institution-wide policies in mind.
The best way to communicate your stance on the use of ChatGPT in your course is a statement in your syllabus. Here are some examples and resources for syllabus language:
From Yale University-- Artificial Intelligence and Teaching: A Community Conversation
From the University of Maryland Department of English-- Prompted By: A Conversation about Writing and Authorship Prompted by Artificial Intelligence