The UK (and others) signed and ratified this treaty in 1929. It is still in force today and has NOT been repealed. The UK is in breach of this international treaty which promises NOT to use war - as a matter of national policy.
Here's the record of who signed up and when http://www.fco.gov.uk/en/treaties/treat ... 1800/01829
Here's the treaty itself http://www.fco.gov.uk/resources/en/pdf/ ... S1/1929/29