Marking and tracing
In order to properly control the flows of arms into and out of their countries, states need to know where the guns are coming from. Tracing involves the systematic tracking of illicit weapons from their source (the manufacturer, or last legal importer, or last legal owner) through the lines of supply, to the point at which they were diverted into the illicit market. If this point of diversion can be identified, preventative measures can then be taken to stop guns falling into the wrong hands.
Recognising the importance of adequate marking, recordkeeping and tracing, the non-binding International Tracing Instrument was agreed at the UN in 2005. This complemented provisions in the binding 2001 UN Firearms Protocol. Implementation has been slow, despite the involvement of Interpol. A key problem is computerisation of records, so that each gun can be linked to its last legal user.