Here's the applicable federal law on it:
33 CFR 159.5 says: "Requirements for vessel manufacturers.No manufacturer may manufacture for sale, sell, offer for sale, or distribute for sale or resale any vessel equipped with installed toilet facilities unless it is equipped with:(a) An operable Type II or III device that has a label on it under §159.16 or that is certified under §159.12 or §159.12a; or(b) An operable Type I device that has a label on it under §159.16 or that is certified under §159.12, if the vessel is 19.7 meters (65 feet) or less in length."33 CFR 159.7 says:"Requirements for vessel operators.(a) No person may operate any vessel equipped with installed toilet facilities unless it is equipped with:(1) An operable Type II or III device that has a label on it under §159.16 or that is certified under §159.12 or §159.12a; or(2) An operable Type I device that has a label on it under §159.16 or that is certified under §159.12, if the vessel is 19.7 meters (65 feet) or less in length."If you want to search out all the other references, you can download 33 CFR 159 from here: http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&sid=86d314715a20ea99670b2d5376c284ec&rgn=div5&view=text&node=33:2.0.1.5.27&idno=33So yes, it is illegal to mfr or sell a boat in the US which isn't equipped with either a holding tank or a Type I or II MSD...but it's also the responsibility of the vessel operator (note that the language is "operator," not necessarily the owner) to keep his vessel in compliance with local laws, whether the mfr or dealer has met his legal responsibility or not. Iow, if the boat was originally sold into waters in which the discharge of treated waste is legal, but is moved to "no discharge" waters--or the waters he's in are changed to "no discharge"--it's the owner/operator's responsibility modify his boat to meet the new requirements. Ignorance of the law is not a defense.