Prior to the French and Indian War, the area west of the Appalachians was French, and the British had no jurisdiction there. The war actually broke out at the Battle of Jumonville Glen when a dispute arose over the actual location of the border between French and British America. After the Treaty of Paris of 1763, the territory became British, as France surrendered all of its claims in continental North America. The Royal Proclamation of 1763 was primarily designed to prevent conflict between the colonists and Indians who occupied the area; it was something of a tacit understanding that this territory was to be reserved for the Indians. So there was no U-turn, it was just an adjustment when new territory was added to the British North American Empire.