Recent IR literature suggests that populist ideology, while primarily a domestic phenomenon, has distinct foreign policy implications, as populist leaders reject Western hegemony, transnational elites, and liberal international institutions. Yet how impactful is this stance, given the potential costs of defying the liberal order? This paper argues that populist leaders can pursue more radical foreign policies only when shielded from international economic constraints – most notably through natural resource rents. The interaction of populism and resource wealth enables a distinct brand of radicalism, combining sovereigntist rhetoric with defiant foreign policy postures and withdrawal from institutional institutions. We evidence this argument through case studies of Bolivia, Ecuador, Iran, and Venezuela, showing how resource-backed populist leaders engage in sharp opposition to Western influence and retreat from liberal international organisations. To test the broader applicability of our theory, we conduct cross-national econometric analyses. Our findings show that neither populism nor resource rents alone reliably predict radical foreign policy. However, their interaction does: Countries with both features are significantly more likely to vote against the West at the UN, use sovereigntist rhetoric, avoid human rights-linked trade agreements, sign fewer investment treaties, and withdraw from international institutions.
