Firefighters in Caledon, Ont., are being told by their union that if they want to fight fires, they'll have to draw a salary for it.

The dispute targets, and may endanger, a breed the town depends on: "double hatters," firefighters who work full-time for a municipality but also volunteer at their local fire hall. Critics of the union's move say it is an attack on that quintessential small-town figure: the volunteer firefighter.

The tension between small-town fire departments and the union has been simmering for years in Ontario, one of two Canadian jurisdictions, along with Newfoundland and Labrador, that doesn't protect the right of firefighters to moonlight.

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Communities as diverse as Ottawa, Stratford and Orangeville have seen double hatters resign en masse or ignore calls for assistance afterunion pressure.

From the archives: Union turns up the heat on firefighters who volunteer on days off

The Brampton branch of the International Association of Fire Fighters (IAFF) sent letters in late September to about a dozen of its members who are thought to moonlight in Caledon, a geographically sprawling town northwest of Toronto, warning them that they could be fined or even expelled from the union unless they resign from their volunteer posts.

The union argues that volunteers, who are paid for calls they respond to, deprive other members of salaried work and violate a professional oath of service. It's why the IAFF constitution bans double hatting, says Fred LeBlanc, a district vice-president with the union based in Kingston, Ont.

"Why some members seem to think the rule doesn't apply to