We explain the Sulphur Emission Control Area (SECA) compliance through analyzing both rational and moral factors for compliance motivation. According to preliminary analysis based on samples and measurements, the compliance rate for SECA is rather good and air quality has improved significantly. As costs of compliance are rather high and penalties for non-compliance rather low for regulation targets, moral motivation factors must be relevant for compliance. Maintaining good relationships with control authorities and peers requires shipowners to comply with the rules for practical and moral legitimacy. Our interviews with Danish, Finnish and Estonian shipowners confirmed that most of them follow the law simply because it is the law, this applying both to current Baltic Sea SECA rules and the future global sulphur emission rules. Obeying environmental law thus has a taken-for-granted status among shipping companies. Almost half of the companies specifically mentioned they follow the SECA rules because they want to take care of the environment, thus having internalized the regulatory content. Some companies see global compliance to depend on efficient controls.