Traditional international relations theory holds that states will join only those international institutions with which they generally intend to comply. Here we show when this claim might not hold. We construct a model of an authoritarian government's decision to sign the UN Convention Against Torture (CAT). Authoritarian governments use the signing of this treaty — followed by the willful violation of its provisions — as a costly signal to domestic opposition groups of their willingness to employ repressive tactics to remain in power. In equilibrium, authoritarian governments that torture heavily are more likely to sign the treaty than those that torture less. We further predict that signatory regimes survive longer in office than non-signatories, and enjoy less domestic opposition — and we provide empirical support for these predictions.