You can use a marker on land with permission as long as the owner controls who is on there at the time and that you are using the markers a set distance away from any public access/right of way. I'm not sure tho if there is a restriction on numbers (probably a bit like what constitutes a riot
) any more than a certain number would probably still come under hse requirements somewhere.
Basically marker use follows the same rectrictions as for an air rifle.
Personally I don't reccon it's worth the risk unless you own the land and can guarantee to be away from all non-involved parties...
the sentence that could be incurred really is not worth it.
Now if we lived in the USA .... yeah dream on...............