Critics challenge international courts for their interference with domestic democratic processes and alleged violations of rule of law standards: they claim that these guardians of the rule of law are not well guarded themselves. These concerns should not be dismissed too quickly as mere disgruntled venting by populist politicians. This article focuses on regional human rights courts and argues that the same interests and values that justify rule of law standards of impartiality, independence and accountability domestically also justify similar standards for international courts. Focusing on the European Court of Human Rights and its doctrine of the margin of appreciation, the article demonstrates how this doctrine may contribute to fulfilling the rule of law but at the same time may also endanger it. This requires changes to the doctrine to ensure that the core rule of law standards of predictability and protection against arbitrary discretion are respected.