The 2006 International Convention on the Protection of all persons from Enforced Disappearance came into force in 2010 and has been ratified by 30 states. It creates a new human right against enforced disappearance, and requires the states that have ratified the convention to create new criminal offences in their domestic law and to adjust their laws on (for example) detention.
The Committee established to monitor implementation of the Convention and deal with complaints under it had its first session on 8-11 November 2011. There is already a UN Working Group on Enforced or Involuntary Disappearances which carries out similar functions.
The UK has not signed or ratified the Convention despite some pressure to do so. The Government appears to support the Convention in theory, and has apparently been looking into what changes to domestic law and what reservations or declarations would be needed in order to ratify it. The UK representative made a statement of the UK’s interpretation of some articles of the Convention to the UN General Assembly in 2006.