I kind of agree with dalen, my sensei always said if you got into it with someone stop them any way you can then walk away, if you do hurt someone, even if you are in the right, oftentimes the police will just see it as two guys fighting and you will go to jail anyway, not to mention the guy who jumped you may sue. so unles you got seriously hurt just walk away, if you dropped the guy or girl who just attacked you, you do have liability if not legally at least as one human to another to check them first to make sure you didnt do fatal damage even if it means just pulling them off the street and making sure they dont choke on their own vomit, at least then if you do go to jail or court they will take into account that you administered first aid to someone who just attacked you. also the one time i did disarm a guy with a knife he practically dove for the knife, i kicked him in the head, he was so fixated on it he didnt even protect his face! generally on the street they will fight to get the weapon back or they will run.