Warlordism means a situation in which there is no rule of law. A warlord rules by rewarding his friends and punishing his enemies.
To break a warlord equilibrium, you need government. That is the Hobbesian solution--a Leviathan that is capable of suppressing the "war of all against all."
I fail to see how getting a Leviathan counts as "breaking" a warlord equilibrium. Why shouldn't it simply be described as "accepting" a warlord equilibrium - you quit resisting the rule of the most powerful warlord, and let him run things?
Arnold admittedly mentions the "rule of law," but neither Hobbes' Leviathan nor most governments throughout history do well by this measure. "But some have," you say? Question: If you can occasionally get a Leviathan to respect the rule of law despite its monopoly, why couldn't you get comparable or better behavior from competing firms - firms that might lose your patronage if they mistreat you?