Should there be such a thing as squatters rights?

I know someone who had the exact same experience. The squatters got in through the dog door. This must have been 2012 or earlier because that year the UK Government passed a law to criminalise squatting (“trespass on a residential property with intent to occupy”) - previously it had only been a tort. 

Ideallly, there should be a multi-tier system, but with a presumption in favour of the owner. Anyone who squats in a property that is normally occupied is not deserving of sympathy and shouldn’t benefit from squatters’ rights. At the other extreme, if a building has been allowed to become derelict or incapable of habitation, the owner should only have recourse to civil procedures, not criminal law. For intermediate cases, different degrees of leniency could be shown - such as, where it’s boarded up, or where the owner is keeping it vacant and has no short-term intention to put it to beneficial use.