Strictly speaking squatting is not a criminal offence if you get into an empty property without forced entry, e.g. breaking or damaging locks, doors or windows. You will be persecuted if you make any damages to the property. And now the Justice Secretary is thinking to make squatting illegal in England and Wales to end the menace of the squatters.

If a property is owned by someone and the owner can get a court order to evict you. If you got a court order to leave, and you refuse to leave, which is illegal.