They are just being daft. Most of the UK has laws or bylaws at least against antisocial drinking e.g. if you're being a twat, violent, homeless, etc you will b

They are just being daft. Most of the UK has laws or bylaws at least against antisocial drinking e.g. if you're being a twat, violent, homeless, etc you will be asked to pour it out and leave, in incredibly rare cases I guess you might be fined but probably not. Just having a beer in public at a picnic with friends is fine and is a national pastime.