Legal Question in Employment Law in California

Re: use of accrued sick leave will cause termination

This reply assumes you work for a California employer within California. It would appear from your question your employer believes these impacted employees are "at-will" employees (i.e., no express or implied contract). Any "at-will" employee theoretically may be discharged by the employer with or without notice or cause. Having stated that, many employers are subjected to wrongful termination law suits frequently for mistakingly believing an employee is an "at will" employee. Based upon the statement of "facts" set forth in your question, it would appear you need to seek the advice of legal counsel. You should start with a local employment attorney who is familiar with "at will" employment principles, the Family Medical Leave Act (and the California equivalent), and employee benefit law.