This chapter examines the decentralized implementation of EU international investment protection policy and its implications for Western Balkan countries. With the Treaty of Lisbon granting the EU exclusive competence over foreign direct investment, a new centralized approach was adopted. However, due to the stagnation of EU-level agreements, investment protection increasingly relies on Member States’ BITs, overseen by the European Commission. The chapter explores how this shift affects Western Balkan countries, especially those aspiring EU accession. It discusses the necessary alignment of BITs with evolving EU standards, including substantive and procedural changes, and the broader implications for investment treaty practices in the region. The analysis highlights the challenges faced by these countries in harmonizing their agreements with EU policies and the potential impact on their accession processes.