Do school administrators have the legal right to search you if you are caught off campus smelling like marijuana?

It depends on the terms of the admissions agreement. Many universities have morality clauses that give them specific rights and require that you live according to specific standards. Violation of those standards can result in disciplinary action including suspension. Perhaps the university does not want "pot-heads" going out into the world to represent them. * Only if you are on the campus grounds at the time of search and only if there is a reasonable suspicion that the student is currently under the influence of a controlled substance.