U.S. begins issuing passports with 'X' gender marker
Special LGBTQ rights envoy celebrates 'significant step'
Special LGBTQ rights envoy moderated activist roundtable
The US is among statement signatories
Dana Zzyym filed federal lawsuit after 'X' gender marker request denied
Government amended regulation after lobbying from activists
Intersex activists also sharply criticized measure
Andrés Manuel López Obrador took office on Dec. 1
Trump says he will "call up the U.S. military and close our southern border"
Anti-government protests have left hundreds dead