Can we deduct a signing bonus from an employee’s last paycheck?

Q: “We have a $3,000 signing bonus for certain categories of employees. The signing bonus is paid in two payments: the first of $1,500 is paid in 90 days; the second of $1500 is paid in 120 days. We have a clause in our agreement that states if an employee separates from the company for any reason before the completion of 120 days, $1500.00 is due back upon employee termination. Is it legal to deduct the signing bonus from the employee provided that wages do not fall below minimum wage?” – Cecilia, California