How large are optimal tariffs? What tariffs would prevail in a worldwide trade war? How costly would a breakdown of international trade policy cooperation be? And what is the scope for future multilateral trade negotiations? I address these and other questions using a unified framework which nests traditional, new trade, and political economy motives for protection. I find that optimal tariffs average 62 percent, world trade war tariffs average 63 percent, the government welfare losses from a breakdown of international trade policy cooperation average 2.9 percent, and the possible government welfare gains from future multilateral trade negotiations average 0.5 percent. (JEL F12, F13, O19)

We examine international regulatory agreements that are negotiated under lobbying pressures from producer groups. The way in which lobbying influences the cooperative setting of regulatory policies, as well as the welfare impacts of international agreements, depend crucially on whether the interests of producers in different countries are aligned or in conflict. The former situation tends to occur for product standards, while the latter tends to occur for process standards. We find that, if producer lobbies are strong enough, agreements on product standards lead to excessive deregulation and decrease welfare, while agreements on process standards tighten regulations and enhance welfare. (JEL F13, F14, F15, L15, L51)