Discharge of raw sewage inside the 3 mile limit has been illegal for 40 years. What the 'no discharge' designation really changes is the ability to discharge through a device such as a Lectra-San.
A friend keeps his boat in Narragansett Bay one dock over from the EPA folks. He had a long talk with them about the discharge issue, and the short story is that the Rhode Island EPA only cares about solids - they're could care less about liquid discharge. So, he had removed the head from his boat. Liquids go into a bucket and over the side. Solids go into a bag for disposal ashore.