In the wake of recent judicial developments surrounding questions of federal preemption of state laws, this Article seeks to explain and clarify the proper preemption analysis that applies to shipping and vessel regulations that impact federal, state, and maritime commerce interests. Each preemption analysis is different, depending on the source of law for the regulation, the nature of the regulation, the class of vessels, and the activity being regulated. This Article identifies the key categories and provides the framework for preemption analysis for each. It provides a reference guide to the preemptive characteristic of promulgated regulations for the benefit of practitioners, regulators, and marine operators. This Article, however, does not provide a comprehensive recitation of the facts and analysis for each case impacting United States Coast Guard regulatory efforts.