It does not matter what Maine's Constitution says.
Why?
Because everything it says is ultimately subject to federal review.
What actually matters is what the US Constitution says.
Any luck on those statistics regarding the 300,000 new immigrants you'll need?
Also, any word on how your private army of 12,000 poll enforcers will be able to violate federal law on June 12, 2018 with impunity?
Or how your referendum will make it onto the ballot in the first place?
Once again you do err, when the US accepted Maine as a state, in 1820, it accepted Maine with it's 1820 Constitution. Now there are some in the State Legislature that would like to amend both the preamble and A 1 sect 1&2, but that would take more than four years and it is only four years till the secession vote.
Look if you don't want to come to Maine and be free, that's fine, but quit trying to dissuade others who might like to be free. Like so many big govt reliant, you just keep beating and hoping to prevail with no facts or basis for fact on your side. We have been at this since 1985, do you really think you are coming up with anything new? Can you really be that vain?