> make use of the ultimate in jam resistance: neutrino transmission. For all practical purposes, almost nothing (including several light-years of lead) will stop a neutrino

Signals aren't jammed by being blocked but overpowered. If you want to disrupt someone's neutrino comms, you don't start building lead walls. You flood their volume with neutrino noise. (I don't know how feasible that is to continuously do over a large volume.)