I'm not certain that is really the case; it might be that the states and Federales just didn't bother regulating cannon, even though they weren't protected by the 2nd Amendment. Be interesting to see what laws DID govern armed ships in American harbors.
Unfortunately, the Commies figured out that lawyers were more dangerous than armies and used 'em against us.
What we really need is Lawyer Control...
Read the constitution. It provides for calling up the militia to defend against invading armies and navies. It provides for letters of marque and reprisal so that civilians can capture enemy warships. Then read the second amendment. Read the Federalist papers where it's pointed out that no standing army could hope to win against a militia that is similarly armed. Read statements of the founders from the time period when the constitution and the bill of rights were ratified. Their concern was whether the people would always be armed heavily enough to defeat any army on earth (including our own), not that the people might get too many scary weapons. Square that with disarming the people or even placing limits on what weapons they should have. An honest originalist reading of the constitution may lead to the conclusion that we may need an amendment to ban civilian nukes.