Direct-to-Device (D2D) satellite communications—where standard mobile devices connect directly with satellites—offer a promising solution to extend coverage and improve network resilience. This paper examines the spectrum allocation and regulatory challenges of enabling D2D satellite services in the European Union (EU), situating the analysis within the broader evolution of International Telecommunication Union (ITU) regulatory processes. While anchored in the preparations for the World Radiocommunication Conference 2027 (WRC-27), the study emphasizes that regulatory developments are dynamic and extend beyond a single conference cycle, ensuring long-term relevance for spectrum governance. The paper provides an overview of satellite communication fundamentals and defines key D2D concepts, including Internet of Things (IoT) use cases and differences between terrestrial mobile bands and Mobile-Satellite Service (MSS) bands. The analysis highlights the current EU landscape for MSS spectrum, particularly the 2 GHz S-band, and its upcoming licensing challenges. It contrasts the EU approach with international developments—notably the United States’ new “Supplemental Coverage from Space” framework and the United Kingdom’s satellite-to-mobile integration plans—to draw lessons for spectrum-sharing models. Technical and regulatory challenges for integrating D2D are identified, and potential alternative frequency bands and spectrum-sharing techniques are explored. A policy roadmap is proposed, outlining short-, medium-, and long-term actions for EU policymakers and stakeholders to enable D2D services. The study ultimately supports the formulation of a forward-looking regulatory framework that secures Europe’s role in shaping the future of hybrid satellite-terrestrial connectivity.