For several hundred years, it has been a basic rule of our legal system that "all crime is local". For another country to seek to punish conduct not performed within its borders has been seen as an unacceptable attempt to undermine the sovereignty and authority of the country of residence of the person accused. The era of colonial power was perhaps an exception to this, but one justified on the basis that the colonial power included all its empire within its own territory.
It was not always so. When the Christian Church held sway across Europe, the canon law was supranational, and breaches of canon law were tried in Church courts, and subject to appeal outside the country of origin. Much of our modern criminal procedure came from church law. But the Reformation in the 16th centuly removed the widespread ambit of this kind of international criminal law. The one crime of universal jurisdiction after that was piracy - armed robbery on the high seas. Any country could try - and usually execute - a person accused of piracy. But developments culminating in the this new century have brought in a new era of international criminal law and procedure.
Available at: http://works.bepress.com/mary_hiscock/1/