Uti possidetis juris is a principle of international law, which states that nations who gain independence from some sort of oppressive or ruling power will have the same borders that they had before they gained independence.
This term first came to prominence when the colonies of Latin America were gaining their independence.
The purpose of uti possidetis juris is to prevent further war or conflict when nations gain independence from some ruling power. Uti possidetis juris prevents newly independent nations from redrawing the boundaries of their nation. If newly independent nations do try to redraw their boundaries, then bordering nations could be drawn into a territorial dispute with the new nation, which could result in war. So this international law attempts to prevent such territorial conflicts or wars from occurring in the first place.