One of the deficits of the international legal system is the way in which respect for, and enforcement of, legal norms is obstructed by political interests (see section 4 here). Consider the case of contemporary Zimbabwe. In a world governed by the rule of law, Robert Mugabe would by now be, if not behind bars, then caught up at one or another stage of a legal process to try to make him answerable for the crimes of his regime. Not only does he remain at liberty and in power, however; political calculations dictate that he must be a participant in the upcoming conference of EU and African leaders in Lisbon.
One of the ways of making an effective reality out of international law is for some states to impose penalties on other states when they transgress. Here, with a man who has shown himself ready to starve the people over whom he rules, the EU organizers aren't even willing to exclude him from an international gathering.