An Article 4 direction is made by a local planning authority in the United Kingdom and exceptionally may be subject to intervention by the government.
For example, it could stop a landowner from holding car boot sales on their land for 14 days per year—a right which they would otherwise have—or could restrict a householder from converting a property into multiple flats.
These exemptions are to ensure permitted development rights related to national concerns, safety, or maintenance work for existing facilities cannot be withdrawn.
[1] Article 4 directions were in the past a rarely used instrument which was not particularly effective, and was difficult to apply as it always required the approval of the Secretary of State.
The 1995 Town and Country Planning (General Permitted Development) Order made significant improvements to the process, and since that time the use of Article 4 directions has increased.