The only way to fire a tenured faculty member is for gross misconduct or gross negligence but not for malfeasance. Even when there is gross misconduct or negligence, it still takes hundreds of thousands of dollars and way too much time to remove them. I believe that we can get good professors without tenure. That's not the answer you get, and if it is, that person shouldn't be there. No one should have lifetime employment.
Contracts are the answer.
As long as you perform, your contract will he renewed.