Countries other than the UK have their own legal systems and sources of law. From a UK perspective this law from other jurisdictions is often referred to a 'foreign law'.
Law created at a supra-national level derived from treaties, case law and custom between countries as well as law developed by international organisations, such as the United Nations, is referred to as 'international law'.
In addition to the primary sources of foreign and international law there is secondary legal information (books, journals etc.) associated with these non-UK jurisdictions.