OVERVIEW
You can suspend users at a course level, in which case they will be able to access your LMS but not the specific course from which they have been suspended.
SUSPEND USER FROM COURSE
Step 1: In the relevant course, on the "Enrolled users" page, click on the gear icon in the "Status" column next to the user you would like to suspend from the course.
Step 2: Set the user's "Status" to "Suspended" and click on "Save changes."
The user will now reflect as "Suspended" on the "Enrolled users" page and will not be able to access your course until you reactivate their enrollment.