No international standard that's for sure.
We have AS4373 2007 here, just a lot of tree workers dont know about it.
Standards for tree care are just that, not a law, ANSI isn't even a law. What it boils down to is local law at the council level or higher laws for protecting heritage/significant trees.
Frankly, if there's no enforcement then how is any malpractice dealt with? Oh, by civil proceedings ... and who does that? The client, and how many do follow through with that?
There's one way around perhaps, and I'm yet to read a case. We have a govt authority called Dept of Fair Trading (DFT). It looks out for shanksters and rip off merchants. Lets say customer asks for tree trim, gets a topping. Now it's possible but unlikely the DFT chase the case as the tree worker didn't do his job to standard. But I'm yet to see one case. You'll likely hear that it's a civil matter and you pursue it yourself.
Then if you are going to pursue it I doubt it's an insurance claim off the tree worker. So if you do win $10,000 case you still have to get the money. And it was a gypsy with a mobile phone, good luck.
The best working examples seem to be those where local law has tree protection and tree work has to be performed to local laws criteria. No local law, no tree protection, you got buckleys mate.
Then you get a group or organisation who take on the absurd task of trying to educate their own and the client. What a waste of resources. Sure education is a good thing but I wonder what sort of buildings and bridges we'd have if the other trades took on this approach.
London Bridge would indeed be falling down.
The answers are so simple that they're almost a joke. Trained qualified people with a licence, local tree laws, and the client like hiring any other tradesman can pretty well be assured of some consistency and a job done to regulation. Not the clients job to know your job, that's your job. Not the clients job to know how deep the electrical trench to the back shed has to be, whether it needs conduit or not, what grade the wire has to be for the span, does it need it's own fuse, does it need a dead man switch yada yada yada .... they just know they hire a qualified licenced electrician.
And if that electrician buggers up he can have his licence pulled, be fined and the org behind it remedied the faulty work.
Simple.