Let’s be clear. The essence of our federal system as it applies to the ordinary citizen is that we are absolutely free to travel interstate. ThesStates, however, have what are called in the United States, “police powers”. The police powers have been described by the American Supreme Court as the “right of self-defence” in respect of such matters as internal order, or the safety, health and morals of the people of the state and they empower the states to act in respect of the self-defence of the citizens of their states where safety, health and morals of those citizens are...