Google-fu:
"A yellow ribbon attached to weapons provides a way to identify members of the self defense force in Tancitaro. Vigilantes took up arms in Tancítaro against a group known as 'Los Caballeros Templarios'."
Most articles I've seen link them to members of the "Self-Defense Council of Michoacán" and we're seeing them in different places not just Tancítaro.
But Tancítaro has been involved in this from early on(they started fighting the Zetas 10yrs. ago) so maybe they've been at it longer and are considered experienced vets so some of them have dispersed into the other newer less experienced forces and that's why we see them mixed in here and there?