Over time, traditional institutional borders become increasingly restricted compared to functional territories. To overcome the exiguity of the territory and take advantage of economies of scale, sub-central governments partake often in interjurisdictional joint ventures to provide public services. Budget resources are then earmarked to finance these ventures and this erodes citizen fiscal sovereignty at the local level. Amalgamation represents a solution to recover this lost control. However, locals tend to be reluctant to amalgamate with other, although neighbouring, social groups. Based on a survey administrated to the members of parliament in two Swiss cantons, this exploratory study identifies what we call the resistance threshold to amalgamation, i.e. the share of the budget earmarked to finance joint ventures above which the decision-maker considers amalgamation a viable solution to recover budget control, even if it erodes social identity. The paper also identifies some socio-psychological and political determinants of the threshold