Strict liability with mandatory insurance covering the maximum credible loss — no liability cap, in a competitive insurance market, not subsidised by the state. This is the only instrument that simultaneously: prices the externality not the transaction (the premium tracks expected damage); self-enforces (binary: the operator either holds a policy or they don't); builds in adversarial verification (the insurer pays out on harm, so they price it correctly and audit the operator); and gives the state no fiscal stake in the activity continuing (premiums go to insurers, not the Treasury). If the maximum credible loss exceeds insurance market capacity, no policy is written and the activity is braked by the absence of coverage.