In the Southern and Eastern Mediterranean (SEMed) region, the transition to low-carbon power must be achieved while ensuring security of supply, affordability and development. Using the Just and Sustainable Energy Transition framework and a neo-institutional lens, we analysed 470 study–country–family observations (2000–2025) across 11 jurisdictions and 7 instrument families to create an institutional mechanism map. Three regularities stand out. Systems performance signals dominate in nine countries, primarily through time-differentiated pricing, settlement discipline and codified connection, queuing and curtailment rules. Financing and integration risks are often addressed together where auctions, revenue-support schemes, published access terms and standardised long-term contracts coexist with system rules. Equity-related signals arise where prosumer compensation and reconciliation rules influence participation and cost sharing at the retail margin. These patterns provide an interpretive basis for sequencing constraint-led reforms in SEMed power systems that target binding risks while respecting fiscal and distributional constraints.