The alternative is to have the states start shutting down FBI and DHS offices and escorting them out of the state, but I don't see anyone having the cojones to do that.
“You need an organization to start resistance....”
Normally, that’s the strategy. It’s not the only strategy though. There was a manifesto floating around the bulletin boards back in the days before the internet, touting a strategy called “O.M.A.R.” : “One Man Armed Resistance”. Basically it was a progression from the idea of resistance cells, already designed to minimize the impact of infiltration, to “cells of one”, to neutralize the strategy of infiltration altogether.
Of course there are certain things that a single person just can’t accomplish, and a bunch of individuals acting on their own are probably not going to act very coherently, so there are definite disadvantages to such a strategy. But it does have the advantage that the opposition cannot neutralize the resistance by means of infiltration at all.