I think it would help make a level playing field in the planning laws. There are too many loopholes in the planning system and many people including myself have to standby and watch yet another piece of land or property destroyed knowing that the planning system will in most cases will not be able to do anything about it.
Make retrospective planning applications illegal for everyone. that would hopefully prevent land being sold and moved onto by gypsies and travellers without planning permission and going before the council committee after the damage has been done, it would also stop others from running business's etc from properties without the right planning permission. There are many infringements of planning regulations happening all the time by people all over the country and to be quite honest it is not difficult to check to see whether you need planning permission for any project so really retrospective planning is not needed.