Can I be fired for not wanting to become a full time employee?

Absent a contract (which can sometimes be created by an employee handbook) or statute which either provides that an employee will be employed for a certain time (i.e. a three year contract) or limits the reasons why an employee can be fired (i.e. a contract which provides that an employee can only be fired for good cause, or a statute which provides that no employee can be fired based o their religion), an employee can be fired for any reason, including refusing to work additional hours.