The problem is that the politicians made unauthorised possession of guns & ammo an absolute offence - you commit it you get done, no excuses.
This has led to the jailing of people who found guns and handed them into the police and a widow who found her husband had hidden a handgun in the house. Since there is no allowance in the law ("without reasonable excuse" is usually written in) judges have no option but to find people guilty.
MPs are well aware of this but are too busy fiddling their expenses to do anything about it.