The state of Oregon allows an employer to make the decision as to whether vacation time will or will not be paid out; however, having made the decision, it is valid for all employees. So if they usually pay out vacation on termination, they must do so for you; if they don't normally pay it out, they don't owe it to you, either.
It is legal for them to have a policy that says they will pay it out in certain circumstances and not in others, as long as they are consistant with that practice.