You honestly don't need the state as a check, all you need is a group made up of volunteers that function like a militia that are well armed. To claim that we need the state as a check is to make the claim that it would be impossible for people to organize themselves voluntarily to defend themselves against aggressors which is simply not the case. Let's just take Rojava as a perfect example where people from different backgrounds and faiths organize themselves against outside aggressors even at the most extreme situations. Check out this link for more information. http://bravetheworld.com/2015/06/02/anarchy-lives-rojava/