The EPA has been asked to regulate emissions from cruise ships, freighters, and other ocean-going vessels. According to an AP article,
Marine vessels are responsible for nearly 3 percent of the world’s greenhouse gases — equal to the amount generated by all cars in the U.S. — and ship emissions are projected to grow by more than 70 percent by 2020 as global trade expands, according to the petitions.
The Supreme Court determined earlier this year that greenhouse gases like CO2, which many believe are responsible for global warming, could be regulated by the EPA. Exactly how this might work for foreign-flag vessels operating outside US waters isn’t clear, but it seems the EPA wants to establish a uniform standard with other countries where cruise ships and other vessels dock.