The Espoo Convention obliges contracting states to take all appropriate and effective measures to prevent, reduce and control adverse transboundary environmental impacts from any activity contingent on the decision of a national authority. This includes the obligation to notify potentially affected contracting parties of such activities as well as to conduct an environmental impact assessment (EIA) that permits transboundary public participation. This essay illustrates the legal principles and procedures stipulated by the Espoo Convention as well as recent developments within the regime’s compliance mechanism, wherein the Espoo Implementation Committee was assigned two reviews of alleged convention infringements. The first case in question, “Rivne”, concerns a Ukrainian power plant whose lifetime extension had been granted without prior EIA and public oversight. The Implementation Committee considered the extension as an activity subject to the convention’s provisions. The second case, “Hinkley Point C”, concerns the planned construction of a nuclear power plant in the United Kingdom and the evaluation of its potentially adverse transboundary impacts. The Committee held that notification was necessary even in cases that exhibited a very low likelihood of transboundary impact.