I was on mainline CO service from DCA-EWR about a month ago, and the pilot read the same message over the PA. He didn't use strong language; in fact, he didn't sound overly convicted for or against the rule - he appeared to be just reading it.
I thought it must just be some pilot who missed the memo.
But now, reading this, I wonder if its more than just that one pilot, or if its more widespread. And if the 30-minute rule out of DCA didn't exist (which it does not, as far as all my research tells me), but you stood up anyway, wouldn't you be eligible for arrest & prosecution at EWR for disobeying a flight crew instruction?
And to take this a bit further, what if they told you over the PA that no one was allowed to use laptops, for example, out of DCA or the plane would divert? Can the crew just make up rules and then hold the pax to them, regardless of whether they are actual rules or not? (I'm certain that TSA would happily arrest anyone breaking the "rule" without asking any questions first.
You know, "national security"... "terrorist threat"... etc.