Here in Mn most munincipalities require licensing and some don't.
The Twin cities has 7 major counties and probably close to 50-75 different munincipalities.
I primarily work in one county sometimes two, i believe that I carry at least 8- 10 annual licenses for different townships.
Im all for state licensing with mandated laws for proper arboriculture. I have plenty of work as it is, but get sick to my stomach when I see some of the hackery around town.
The city i live in does not require licensing, and it drives me nuts to see these guys in my own neighborhood. As a matter of fact last summer, i was standing at the bottom of my driveway with 2 other certified arborists(just getting back from fishing) ,when down came the street a loud, rusted out, dilapitated flat bed truck. The truck slowed as it approached and swerved over to our side of the road, the driver see us chatting and here comes his pitch "you guys need some tree work?" It was dead silent for one second, my partners and i all looked at each other and we all busted out into a hysterical laugh. The driver just let his foot of the brake and rolled away down the hill after not one of us said a word to him, I wonder why.
These guys drive 1-200 miles into town, rent a motel for the week, and knock door to door from sun up to sun down.
although in my town a license is not required to do tree work, it is required by law that you obtain a peddlars license for any type of door to door solicitation.