Here is a list of 6 stations in Maine that supposedly sell ethanol free. However they are all only 91 octane.
Ethanol-free gas stations in the U.S. and Canada
It can't be illegal to run ethanol free. Ethanol isn't any better for the environment than e10.
... How do they know what fuel you use?
If it's illegal to run it in Maine, it wouldn't be able to be sold there... right?
A cop would have to have a warrant to pull someone over and search the car for the receipt to prove they purchased and used illegal gas, they won't have a sniffer for the tank, even then it would be mixed with what they bought last time.