A wise man, who has an arse photo fetish, once told me that "As for 'legality', the common law allows one to go where one wishes so long as there is no criminal intent or breaking in, and most land 'ownership' is the result of theft from the common wealth by the enclosures (or former robber barons) so I'd not take the protests of landowners too seriously, never mind that the nail setter is a 3rd party with no rights in the matter."