Tell them(the ISA), if he is using the logo and has never been, that is wrong. They will go after them, pretty harshly from what I understand. But, you can also elect not to be published on the site, why some guys do that, not sure, but ya can. Also guys let their ISA membership run out but they are still a CA. If they have a add in the phone book,etc or have it on the trucks, take a pic. The ISA will be able to tell you if they are. If they are bogus, just get out of the way. Some guys have Arborist in their names, but are not CA's, no biggie, there are many top notch guys that are epic level Arborist, but are not Certified thru the ISA. They are still Arborist.
So when checking on that stuff, keep that in mind. Now,if they are hacks, and have ISA stuff plastered everywhere, take em out!
I don't think Dr Shigo was a CA, elders?
We have a guy that rolls around in your typical white pedophile van, with those mail box letters "Dr Tree" on the side........crooked! He tells people he is a certified tree surgeon! Real creepy looking guy, not even hack level, totally pathetic!