Can you terminate an employee before the end of their 90 day probation period and deny them unemployment compensation?

The employer neither denies nor approves Unemployment Compensation.

Another answer:The above answer is correct in that the state's unemployment agency decides whether or not you get your benefits. However, your question is valid where the employer, by shortening your working period, may actually make you ineligible for the state's requirement. It would depend on the worker's employment agreement, the employer's record of similar actions (possible violations of law), and your own state's ruling in these matters. Check these questions out with your unemployment office. Good point!