From the Lincolnshire Police website:
"Hare coursing in itself can be legal.
The season runs between the first of September until the last day of March and there are legally run coursing clubs such as The East of England Coursing Club which run well-organised events.
Hare coursing becomes illegal if carried out on a Sunday because it is illegal to take game of any description on a Sunday. It is also illegal to course on land with dogs without the permission of the landowner. Those who do so are trespassing and committing the offence of poaching. "
http://www.lincs.police.uk/depts/rural/coursing.shtml