Secessionist movements, when they resort to violence, can undermine the stability and threaten the security of states. Institutional designs, like power sharing, that mitigate issues associated with secessionism may be instrumental for states that contain potentially violent separatist groups. Strategies to share power include regional autonomy, which diffuses power to local levels, and complex power sharing, which centralizes power among elites at the national level. Support from external actors may prompt or further enable violent rebellious activity from separatist groups, thus derailing the potentially pacifying effects of these power sharing institutions. While past work has considered the impact of secessionist activity on governance and foreign actors' roles in intrastate conflict, this paper considers how these internal and external factors converge to influence rebellion. I contend that secessionist activity is incited by both regional autonomy and complex power sharing, especially when foreign support is involved. To test these propositions, I employ quantitative methods, specifically logistic regression. I find a positive and statistically significant relationship between the interactions of political institutions with outside aid and secession, which provides evidence for my theoretical propositions.