There are two general types of “Cossack” in contemporary Russia. There are the groups which generally are culturally-oriented; these are the people I know via Andrey Karimov’s group. There are also the groups which have closer links to the Russian state and which, in south Russia and elsewhere, play a more formal, paramilitary role, including policing.
This latter group have until now been unarmed (or at least, without firearms; famously, they have been carrying nagaika whips, such as those used on Pussy Riot at Sochi).
It seems this is now changing: Stavropol Cossacks were allowed to wear civilian weapons and to use force.