The requirement to declare that I am lawfully armed infringes on my right to remain silent. You are correct that it does not infringe on my right to be armed, at least technically, but it does involve trading in one right for another.
First of all, there is no "right" to remain silent. There is a right not to incriminate yourself. If you are not violating the law, there is nothing you can incriminate yourself about.
IOW, if you are legally carrying, informing can't incriminate yourself. If you are illegally carrying (prohibited location) then the law cannot compel you to inform.
Even assuming we want to accept a right to remain silent: It is a very small infringement on one right, for a much larger gain in another.
Or, if there is already a requirement to inform if you carry on a permit (is there in Maine, I don't know), then there is really no loss of right to remain silent from current statute, simply a huge gain in the RKBA.
Politics is the art of the possible, and the perfect can far too often be the enemy of the very good.
Imagine this scenario, ..... As others have pointed out this duty to inform serves no purpose but to entrap those lawfully armed.
The duty to inform is far from perfect. However, it was deemed necessary to get the support to pass Constitutional Carry in Alaska nearly 12 years ago. In Alaska they changed the definition of the crime from "carrying without a permit" to "carrying and failing to inform an officer when contacted". I'm sure that if the scenario you've described is a real danger it would have come up in the Alaska over the past decade-plus and we'd gain some insights. How many instances have occurred in Alaska in nearly 12 years? I suspect the answer to that question is too few for anyone to have even bothered trying to remove the duty to inform from the law.
Which brings up the next point: Incrementalism. About 15 years ago Utah moved to recognize all permits nationwide without regard to whether the issuing State recognized our permits, whether the requirements were similar, etc. We just recognized all permits. In order to gain the last couple of votes needed to gain final passage, an amendment was added to only recognize permits for 60 consecutive days. I was very unhappy at the legislator who did this. He explained it was the only way to assuage a couple of colleagues who worried about Utahns skirting our requirements by getting permits from other States. He also assured me the 60 day limit would be repealed within a couple of years. Two years later, the same law enforcement agencies that had created the FUD that lead to demands for a 60 day limit were quietly encouraging the 60 day limit to be repealed as entirely unnecessary and unenforceable. How do you prove someone hasn't left the State--however briefly--sometime in the last 2 months?
I learned a valuable lesson. Getting Utah to recognize all permits opened the flood gates of other States recognizing our permits. It helped set the stage for States to emulate us in recognizing all permits. It was a HUGE win for RKBA not just in Utah, but ultimately across the nation.
That 60 day limit was a minor annoyance that was never enforced and went away quietly in fairly short order.
A duty to inform is a bigger deal. But to get Constitutional Carry? A small price to pay; really not even a price to pay, just not getting everything you'd like...today.
If it is a problem it can be repealed. If it isn't a problem, it can still be repealed at some point.
Congrats to Maine.
Charles