What is the furthest point from land at sea where individual U.S. state laws apply?

Question

I wondered to myself if there was a specific point within the 12 mile US territorial sea where individual U.S. state law ends and only federal law applies. For example, could an individual/business create an offshore site that is just outside of the local state's legal reach but still under federal law? To my surprise I could not find anything general like: "State law ends 3 miles from shore" or "State law ends 1 mile from shore". Apparently there's ambiguity.

Found a summary here:

There has been tension for decades between the federal government and the states over who has control of the waters out to the three-mile — and more recently 12-mile — limit. The tension has been largely over control of mineral rights rather than how other laws are applied. Offshore wind and state laws

Is there a line at all?

I'm confused... if it's unclear where state laws end and federal law begins how do local authorities even know when to call the feds when they find something suspicious/"criminal" offshore?

How do individuals even know which, if any, state laws apply when they are offshore? But remember that my question is about the border line(s) so saying simply that there's a list of water patrol laws for a particular jurisdiction would not (in my view) answer the question.

I found an example of a kind of border in "The Marine Unit members are also cross-certified Immigration and Customs Enforcement Officers, and are empowered to enforce federal regulations far beyond the limits of State of Florida jurisdiction." Marine Unit, manateesheriff.com. But it doesn't really answer the question.

Answer 1

The answer is more complicated than you may think. The over riding controlling authority is the Law of the Seas treaty signed by almost all nations but not ratified by the US (mainly because the LOS requires equal distribution of mineral wealth in the oceans). A lot of what the LOS covers is what is called the COLREGS which are basically traffic laws for vessels on the oceans. But COLREGS are applicable in some, but not all US federal, state, and local harbors. While the US Coast Guard is the primary enforcer of these laws in the US plenty of other law enforcement agencies have agreements with the USCG to enforce the rules. While you mentioned a local county agency that has agreements to enforce this, and other laws, so do a host of other agencies.

In Florida the FWC is the primary enforcement agency for Florida laws and has an agreement with the USCG and other federal agencies to enforce not just Florida laws but US laws as well. One historic area of conflict has been fishing laws. The US claims a 200 mile economic zone and enforces fishing laws, which sometimes conflict with Florida laws (things like how big a fish must be and how many you can catch and when you can catch them). The FWC has a much greater presence on the water and the USCG does not really deal that much with fishing. On the other hand the USCG spends lots of time with drug interdiction and illegal alien interdiction.

As an example of how convoluted this can get I was in the Dry Tortugas when the FWC boarded a commercial fishing boat anchored close to me. The Dry Tortugas is a National Park so under federal jurisdiction and the fishing boat had anchored rather late at night and turned on it's working lights and and was loudly running a water pump during turtle egg laying season so the rangers in the park called the FWC to come down hard on the boat. The only violation the FWC found was a pistol on the commercial boat (firearms are prohibited in the National Park).

Another example is that according to Florida Law a boat in a recognized anchorage on a mooring ball does not need to display an anchor light after sunset. While Boot Key Harbor in the Keys is a recognized anchorage run by the city of Marathon it is under COLREGs and you must display an anchor light on a mooring ball; something that I have seen enforced by both USCG and FWC.

On the East Coast of Florida in the crowded ICW both city and county LEOs in boats enforce things like speed limits and boating while under the influence; not to mention drug enforcement.

Bottom line is while federal, state, and local laws are not always the same there are wide spread agreements that agencies from all three levels of government can and do enforce each others laws.