There might be a covenent to stop it and councils can in some areas also stop you but it would probably have to be in a conservation area. If you use them for commercial use then you may need planning consent for a change of use. Have you had a problem?
cant see there being a problem unless you have an oversize trailer or horsebox. only a guess, but there are rules about steeling other peoples sun light !
stanleyman, covenants are terms within a contract - perhaps you are refering to statutes, bylaws or statutory istruments?, which there are none. This would come under the Tort of 'Nuisance' which could either be private (brought by the individual)or public (brought by the council) - The specifics of such a nuisance would be in relation quiet enjoyment and anstraction of light. There are a number of other ways in which this could be legally pursued, such as pollution etc.