This paper examines the eect of cross-border lobbying on domestic lobbying and on external taris in both Customs Union (CU) and Free Trade Area (FTA). We do so by developing a two-stage game which endogenizes the tari formation function in a political economic model of the directly unproductive rent-seeking activities type. We nd that cross-border lobbying unambiguously increases both domestic lobbying and the equilibrium common external taris in a CU. The same result also holds for FTA provided taris for the member governments are strategic complements. We also develop a specic oligopolistic model of FTA and show that taris are indeed strategic complements in such a model.