Can international courts influence state policies and facilitate interstate cooperation? Existing literature argues that they can. Courts can make cooperative outcomes easier for states by formulating or endorsing rules around which state expectations and practice can converge. While it is widely assumed that court rulings may become focal points and play a role in harmonizing state practices, we know little about the conditions under which they have such an effect. We suggest that court rulings can often have an opposite, defocalizing effect, which may durably harm the prospects of convergence around what the law requires. We introduce defocalization as a process and discuss its possible types and implications. We argue that defocalization may be driven by incongruence of court rulings with existing treaty law and state practice and inconsistency of rulings over time. We illustrate our argument by examining the effect of key judicial rulings on the convergence of state views about the appropriate maritime delimitation rules by relying on an original dataset. Our findings show how defocalization unfolds and suggest that complexity can accumulate over time through legal rulings that are incongruent with existing state practice or treaty law, and can be maintained through inconsistent court decisions.