In this chapter, a general assessment of the current regulations adopted in the acquis communautaire to reduce greenhouse gas (GHG) emissions from the Maritime Transport Sector (MTS) was carried out. In this context, the research is discussed in two sections. In the first section, the general features of the Emissions Trading System (ETS), which the European Union uses as a legal instrument to reduce GHG emissions in combating climate change, and the preliminarily work on including the maritime sector in the ETS are evaluated. In the second section, the Directives and Regulations regarding the inclusion of the MTS in the European Union Emissions Trading System (EU ETS) and the Monitoring, Reporting, and Verifying (MRV) mechanism of GHG emissions in this sector, the use of renewable energy sources and the reduction of fossil fuels are reviewed. As a result, it was found that the European Union determined strategies to ensure that all sectors of the economy, including MTS, contribute to achieving the targets set out in the Paris Agreement and Regulation 2021/1119 (the European Climate Law). Another strategy followed by the European Union, specifically in the MTS, is to adopt domestic regulations in this field in a way that affects the global MTS in order to mobilize the International Maritime Organization (IMO) to take global measures to reduce GHG emissions from the MTS.