The "Oh, yes they can!" bit is enshrined in the rather bizarrely named Protection of Freedoms Act 2012
s 54 prohibits clamping and the like, as originally promised by Bliar. s 56 empowers the recovery of parking charges. Schedule 4, sets up a legal framework for the recovery of those parking charges. I've not looked for loopholes but I suspect it's in duck's orifice territory in terms of impermeability. It was framed after a lot of lobbying from a powerful lobby. (Clue: the govt which is hell bent on liberalising the yellow line enforcement of street parking to gain a bit of popularity from the motoring lobby, was happy to risk alienating motorists to gain the "support" of the hedge funds etc which tend to own the retail car parks. ) http://www.legislation.gov.uk/ukpga/201 ... /4/enacted
Not much use to the private person who finds a car hogging their driveway, because they'd be unlikely to have got the notices etc in place in anticipation and if they did anticipate it, the easiest thing would be to prevent it with some sort of obstruction. The owner of a shop near here who seems to be plagued with people parking on their small car park while visiting the neighbouring pub and who then leave the cars overnight deploys a line of kerbstones each evening and shifts them the following morning.