This article points to how there is more to the "peace vs. justice" debate than the influence/effects of international law. Most influence - inevitably and obviously - comes from states who have a say in the conflict (and that does not necessarily mean the conflict-ridden state).
And state intervention can be detrimental to the pursuit of international law.
This article leaves out, probably with the intention of confining its argument, questions of traditional justice and the debate around that and "peace vs. justice." In the case of Libya, it's not so much traditional justice as state sovereignty. The question this article mentions is the debate between Libyan courts, which claim they can try the criminals, and the ICC. But the questions of reconciliation and democracy-building are left out. After a civil war, would national courts or the ICC have a greater positive effect on reconciling the different warring parties during the war, or will neither have an effect? In the "peace" portion of the debate, it's important to look not just at the courts' influence, but at what else is necessary to solidify peace, reconcile a divided society, and promote the development of democratic tendencies and institutions.