Chapters 1, 4, 15 and 23 of the Statute of Marlborough 1267, an Act of the English Parliament, are still in force in the UK.
Chapter 1:
criminalised the taking of “revenges” or the
levying of distress without first obtaining a court order.
Chapter 4:
prohibited the taking of distrained goods
or belongings out of the debtor’s home county, particularly where the removal
was carried out by a landlord against his tenant
Chapter 15:
made it unlawful for anyone to distrain on the public highway
Chapter 23:
made it illegal for “fermors” deliberately to “make waste, sale, or exile” (without written permission) of any house, woods, men or any other thing belonging to tenements demised to them.
They were considered for repeal by a Law Commission report in 2012, but were found to still be relevant.
(Quotes are from the above report; see also here, here and here.)
UPDATE, Jan 2016: A subsequent Law Commission report found that chapter 15, and part of chapter 4, have now been superseded and can be repealed (though at the time of writing, this has not yet happened). Chapters 1 and 23 "appear to have continuing value".