The doctrine of colourable legislation is based on the maxim "What cannot be done directly cannot be done indirectly". It means that a legislature cannot do indirectly what it is prohibited from doing directly by the Constitution. If a legislature, under the guise of legislating on a subject within its competence, enacts a law that in reality encroaches upon a subject outside its competence, the law is considered void as "colourable legislation". The true nature and character of the legislation is examined to see if the power has been used legitimately or as a cloak for an unwarranted purpose.