I am not knowledgeable of English laws, but poaching was crime in Czech lands since 14th century. It has to do for overall protection as overkill became a huge problem in medieval times and caused extension of many species in Bohemia (wolfs, European bison, lynx, bears, and elks). Poaching was also defined as hunt outside legally defined hunting season (Sept-Nov). Even wealthy noblemen were fined for violating laws until 1627. Fishing was also on permit where hundreds of ponds across Bohemia were publicly owned, often by municipality, not by manor or landlord. Poaching was problem, because it destroyed expected source of food in medieval times where fish was important staple diet. Again, laws were implemented to regulate and to benefit a greater community. Anti-poaching and forest preservation laws in Bohemia are actually one of the oldest legal documents in that country.
Yes, the lion was living in reserve and was lured out by bait out, so he could be hunted and killed.