If for some reason the authorities wanted to evacuate a street (suspected bomb for example) and someone refused to leave their house, instead taking their chances at home, what would the authorities do. Would the police come around and break your door down and forcibly remove you? Would you be charged with anything?
i suppose if they person was mentally incapable of making the decision to move then authorities would take action. If of sound mind (can you really be of sound mind if you refuse to evacuate?) they would remain in their property. Though would they expect emergency services to help them if there were repercussions?
But unfortunately, dotty, in order to support a charge of obstruction the officer has to be carrying out "lawful" duties. Forcing someone to leave their own home - even if it is for their own protection - is not lawful, so the charge could not be brought (or if it was,it would fail).