not only is it not mandatory, it's fairly easily spoofed and has been for the sake of subterfuge in the past[0] [0]: https://www.securitycouncilreport.org/atf/

not only is it not mandatory, it's fairly easily spoofed and has been for the sake of subterfuge in the past[0] [0]: https://www.securitycouncilreport.org/atf/cf/%7B65BFCF9B-6D27-4E9C-8CD3-CF6E4FF96FF9%7D/s_2019_171.pdf https://www.securitycouncilreport.org/atf/cf/%7B65BFCF9B-6D2...