I've got a country in my world where its reason for existence is to provide a haven for rogue magic-users from a continent-spanning mage's guild. Although ruled by a council of warlocks, government throughout the country tends to be locally-focused and somewhat laissez-faire, with political muscle only being flexed when something drastic happens (e.g. disruptions to commerce, the feuds of wealthy families escalating out of control, etc.).

As I have it written, I feel a bit like I've worked myself into a corner: I'm wondering how this country would plausibly raise an army in the face of invasion, since there's no monarchy or nobility like most of the neighboring countries. The mage's guild hates this country and wouldn't be above manipulating its neighbors into war with it if doing so meant the rogue magic-users living there couldn't escape the guild's grasp anymore.

I'm thinking of writing in a system of sheriffs with authority from the warlock council to conduct some kind of shire levy, but I'm wondering if there are other real-world or fictional models for conscription that might fit with my vision.

Am I overthinking this? Is there a way this country could keep itself safe from the prospect of conventional war without the ability to field an army?