What would be a fair and deterring disciplinary sanction for a student who committed plagiarism? As a program director for a Masters degree in a business school, I am curious to know about higher education policies regarding disciplinary sanctions for plagiarism. This is for both official rules and in actual cases.
I am most interested in the cases where the characterization of plagiarism is not a black and white situation (as is often the case), but the stakes are not minor. To imagine an abstract case: plagiarism committed on a part of a final dissertation. How can disciplinary sanctions scale, before going all out with suspending or expelling the student, while remaining deterring?
If you wait until the very end of the program when a student submits a thesis to check for plagiarism, then you've set up a situation where a student can cheat through the program and then gets caught at the very end.
An alternative approach would be:

Teach students about plagiarism and other academic honesty issues early in the program.  Give them fair warning that plagiarism can result in their being expelled from the program.

Include assessments of students writing throughout the program and check this writing for plagiarism.  If you catch a student committing plagiarism on one of these assignments, give them a strong warning and perhaps penalize their grade.

Require students to submit draft versions of their theses for evaluation and feedback from the supervisor. Check for plagiarism starting with the first draft.

Some central office should keep track of incidents of cheating so that penalties can be increased for repeat offenders.  This is particularly important because otherwise a student might cheat in classes with different instructors and receive warnings from each of them.


The basic idea here is that the consequences for misbehavior should be explained in advance and punishments should escalate with each new offense.  If a student has been warned and suffered a grade penalty on the first offense, then failed a course and had to retake it on a second offense, then it should come as no surprise that they are expelled from the program for a third offense.
Since the potential consequences are quite severe, it's also important to offer students a reasonable opportunity to appeal their punishment for cheating.  There might be a committee charged with considering student appeals.
My institution and many others in the US have systems like the one that I've described above.  In my experience, many students who receive a strong warning on a first offense take that warning to heart and have no further problems.  Other students become chronic offenders and suffer the full consequences.