This weekend in Chicago, President Obama will gather with more than 60 heads of state to hold NATO’s 25th anniversary summit. He and other leaders will convene as a Western-created system of international justice – enforced in many places by NATO – has grown stronger, and raised expectations of accountability around the world.

This week, Bosnian Serb general Ratko Mladic finally went on trial in The Hague for war crimes in Bosnia after evading justice for 17 years. Last month, former Liberian President Charles Taylor was convicted of aiding and abetting war crimes by a separate international court. And in a surprising example of the spreading expectation of international justice, protests among the Syrian diaspora have included signs demanding Bashar al-Assad be sent to The Hague.

At the same time, as people around the globe see war criminals brought to justice, they want to see the world’s most powerful armies held accountable as well. Outside the U.S. and Europe, there is a growing sense of a two-tiered system of international justice. The West puts others on trial for war crimes, the argument goes, while exempting its own forces from scrutiny.

“There is a contradiction,” said Richard Dicker, the head of Human Rights Watch’s International Justice Program. “As the reach of justice extends further and as expectations of justice increase, the shortcoming in the uneven landscape – the uneven application of law to all – becomes more stark.”

Some of the perceptions are exaggerated. The U.S. and NATO are not evil incarnate, nor are they perfect. A recent examination by Human Rights Watch, for example, found that the seven-month NATO bombing campaign in Libya killed at least 72 civilians but that the alliance took major steps to try to avoid such casualties. Taylor and Mladic, meanwhile, went out of their way to kill civilians.