"...its mere existence may encourage good behavior"

But the key weakness of the Geneva Conventions is that the rules that currently exist are inadequately monitored and more seldom enforced. Without an independent monitoring mechanism capable of making informed, systematic, nonpartisan claims about what has happened on the ground, it is all too easy for countries to exploit the gray areas in humanitarian law. Consider drone attacks in Pakistan, which are criticized for having an undue impact on civilians. No independent body is responsible for systematically counting how many civilian casualties they cause. Nor is there any international institution to aggregate other relevant numbers -- for example, civilian casualties from non-aerial attacks worldwide -- for comparison. Instead, journalists and think tanks produce wildly conflicting estimates, relying on non-comparable sources and talking past one another. The discussion over drone use is thus stalemated, and it is left to the allegedly offending government to determine whether, in its estimation, its actions are justified. 

Foreign Affairs: War Crimes Reporting After Goldstone, May 9, 2011