In Central and Eastern Europe (CEE), energy arbitrage has evolved into a complex legal discipline, particularly influenced by market coupling and cross-border capacity allocation. This transformation has been significant since the integration of Ukraine's electricity system into the broader European market, which has created new opportunities for traders. However, it has also introduced challenges that require a deep understanding of legal frameworks, compliance, and contract management. The region's unique position between mature EU markets and emerging demands has made it essential for traders to navigate the intricacies of capacity allocation and auction participation effectively. Market coupling has been a key factor in enhancing the efficiency of electricity trading across borders. Traders must grasp how coupled algorithms utilize available cross-zonal capacity and how congestion impacts pricing. In CEE, this is particularly crucial due to the interplay between established EU markets and the growing demand from Ukraine and the Balkans. The ability to evaluate whether the price spread is executable hinges on a trader's understanding of legal risks, nominations, and balancing responsibilities. This knowledge is vital for capitalizing on the liquidity and supply opportunities presented by neighboring markets like Hungary, Slovakia, and Romania. Participation in Joint Allocation Office (JAO) auctions is not merely a technical requirement; it forms a critical part of the legal architecture governing energy trades. The auction framework dictates who can participate, the necessary documentation, collateral requirements, and the allocation of transmission rights. Furthermore, it outlines the procedures for handling curtailments, compensation calculations, and obligations in changing market conditions. Winning capacity in these auctions is just the beginning; traders must also manage a comprehensive chain of contracts and responsibilities, including purchase and sale agreements, balancing responsibilities, and payment settlements. The lessons learned from the integration of power markets in 2025-2026 highlight that the profitability of energy arbitrage is closely tied to the robustness of the legal architecture. While market coupling enhances efficiency, it also intensifies competition for remaining price spreads. As Ukraine's integration into the European market unfolds, traders must maintain disciplined compliance and effective contract design to navigate the evolving landscape. Legal support is essential for connecting commercial models with capacity allocation, auction participation, and regulatory risks, ultimately enabling traders to secure their profit margins in a coupled and regulated power market.