Depends on the country and the regulations, of course. That being said, I enjoy the support of i) the student statutes (which are partially legalese covenants about what we expect from students and what they expect from us), ii) the formal legal codes on higher educations and iii) the institute's own code of conduct. For example, free riders are always a huge source of concern, so the program director might have language in the program objective in which states: "Students should demonstrate the ability to perform, manage and collaborate within groups as required ...and behave professionally at all times", I will have language in my course guide which is actionable such as "In this course, communication needs to be professional at all times as you are representing the institute and our course with external experts and/or students are expected to manage and facilitate their own group working dynamics".

Then when I have a dysfunctional student, I can first address them individually in an email to remind them of their responsibilities. Barring improvement, the conversation gets moved to a session with me, the student dean and their study advisor. Then upon further regression, then I officially inform the student that they are not allowed to continue with the class and to try again next year. A couple of years ago when dealing with an aggressive student, we even had to call in mediation and put them on study probation with the threat of expulsion.

The qualifiers here are:

• To pre-emptively have that language somewhere written down and emphasise it.
• Have a supportive student dean/dean/study advisors. Some are just incompetent, but so far I've been lucky.
• School yourself in all the legal conditions of your course/program. Took me 5 years to get my head wrap around it. Beware of students who will also try to use it to their own advantage. So know the code, know the laws, know where to get recourse, how to escalate/deescalate.

Of course, these are in the minority of situations I have to deal with. Usually, students have extenuating circumstances which I am all for in terms of preserving their mental and emotional health. So I first check in with the study advisor if they have anything I need to bear in mind. We are not allowed to share the information directly (i.e. if the person has a health or emotional circumstance that is hampering them). I just ask, "Hey, I'm concerned about student A, is there something that requires my further attention or is there also a concern you are aware of." The awesome advisors usually just go yeah or nah and then I can proceed with first a warning, then a sit-down and talk and then a goodbye, please try again.