Governments shall prohibit by law all extra-legal, arbitrary and summary executions and shall ensure that any such executions are recognized as offences under their criminal laws, and are punishable by appropriate penalties which take into account the seriousness of such offences. Exceptional circumstances including a state of war or threat of war, internal political instability or any other public emergency may not be invoked as a justification of such executions. Such executions shall not be carried out under any circumstances including, but not limited to, situations of internal armed conflict, excessive or illegal use of force by a public official or other person acting in an official capacity or a person acting at the instigation, or with the consent or acquiescence of such person, and situations in which deaths occur in custody. This prohibition shall prevail over decrees issued by governmental authority.