Hi @MartinOHalloran, thanks for your question! There are a few ways to approach this by changing course or enrollment status through SIS Import. If you want to keep the course active in your instance for Admins, but remove access and visibility for enrolled teachers and/or designers, you could change their status to "deleted" in using an enrollments.csv. If you want to remove the course entirely from your instance, including from the Admin Courses Tab, you can change the course status to "deleted" using a courses.csv. In this case, the course is not hard deleted, as it's retrievable by running a reverse SIS Import, but it will be removed from your instance and Admin view. If you are new to this process, we always suggest testing CSV files in your test or beta instance prior to uploading in production.
You may also want to check out the Canvas Archiving Solution provided by our Partner K16. I hope that helps to provide a few solutions!