I am adamant that when I buy a pint of beer, I get a pint of beer. Ladies certainly get their 175ml of wine, there is a line on the glass to prove it and Grandpa gets his 25ml/35ml measure of whisky from the Optic.
This is not something that needs additional legislation - it is a basic Trading Standards and Weights and Measures issue. It just needs to be enforced. However, if it is not being enforced, then perhaps legislation should be brought about and enforced with fines on the landlords, pubs, Breweries or pubcos as necessary.
I would like to know who came up with 568ml actually only being 511.2ml. Surely, no, surely not the pubcos? Surely they don't want to maximise their own profit margins, surely not, please tell me they didn't? These companies are totally honest and not into ripping off the beer drinker. They have NEVER EVER attempted to fleece their customers. NO, NEVER!