To resist an organized group, you communicate the problem (in an anarchist society, communicating the problem of a nascent state seems like the easy part), present evidence of the nature and severity of the problem, and ask people and existing organizations to mobilize.
Whether the next step is obstructing the state peacefully or mass production of munitions, would already depend on how bad the state has got.
Came here to post this and say “finally”, but someone had already noticed. :)
There’s a quote that’s probably not from Churcill, but is frequently mis-attributed to him (the actual source is probably Abba Evan, an Israeli diplomat visiting Japan). The distorted quote says something that’s appropriate today: