In legal terms, illegal and unlawful are not synonymous. In the UK, trespass is only illegal in certain circumstances: https://cps.gov.uk/legal-guidance/trespas

In legal terms, illegal and unlawful are not synonymous. In the UK, trespass is only illegal in certain circumstances: https://cps.gov.uk/legal-guidance/trespass-and-nuisance-land https://cps.gov.uk/legal-guidance/trespass-and-nuisance-land Beyond that, it's only unlawful.