Lately I've been on several flights where the flight attendants had to talk sternly to passengers that were getting up either just before landing or just after (which is quite obvious to everyone since the talking to is done over the PA system).
Now this made me wonder what FAs can do if the passenger just refuses to comply? Can FAs get up and forcefully seat passengers (would they have to talk to the pilot first to abort the landing)? If not, are there any circumstances where the FAs can/should/must unbuckle during a landing?