Which regulated professions? Trade unions still require work for their members to do. If there's a recession and say a construction slump, it doesn't matter how high or low the union's regulations are for their members, if there's no work, there's no work.

Medical doctors are a special case, but eg iron workers theres the official list people get called up from, but you're not getting called up from that list if there's no work. You get work through knowing the right person aka networking. Which is where software engineers find themselves today.

> Which regulated professions?

All other engineering (civil, chemistry, mechanical, electrical, ...) and semi-engineering (architecture) disciplines.