In international relations, short-run incentives for non-cooperation often dominate. Yet, (external) institutions for enforcing cooperation are hampered by national sovereignty, supposedly strengthening the role of self-enforcing mechanisms. This paper examines their scope with a focus on contingent protection aka tit-for-tat in trade policy. Highlighting various strategies in a partial equilibrium framework, we show that retaliation of non-cooperative behaviour by limiting market access works as a disciplining device quite independently of supply and demand parameters. Our empirical findings are consistent with the theoretical results in that countries more frequently involved in WTO-mediated disputes entailing tit-for-tat strategies pursue on average more liberal trade regimes.