Where I live, restaurants have to be quiet after past 10pm both indoors and outdoors if they have outdoor tables for example on the sidewalk or terrace. I've been told off for talking too loudly in a group of 4 when sitting outside so a bigger group of loudmouth drunks would certainly be thrown out or told to come indoors. I think this is a non-issue. Not to mention that most restaurants like this are anyway in dense neighborhoods which have a higher noise floor.