Joel's staff hurt the customer. Not delivering your work until paid is one thing. Reverting the site is totally unacceptable. For one thing, it's use of access you were granted to help the customer to hurt the customer. I wouldn't be surprised to see CFAA prosecution for it---and despite the need to reform the CFAA, this is something that ought to be a crime.
If a tradesman does work on some other Donald's house and doesn't get paid, he can't go remove or undo the work---he can place a mechanic's lien or otherwise go through the courts. We don't accept self-help that harms another, no matter how unfair the dealing was.
There are a bunch of legal acts that explicitly give tradesmen rights to recover materials and equipment installed e.g. in a customer's building in case of nonpayment.
As currently worded (AFAIK, IANAL, depends on your jurisdiction, etc) these acts do not apply to websites in the same manner.
My reaction back was poor: in my email back I told him I was stopping all work on the project and reverting his website back to his old theme until he sent payment.
It seems that after Donald's first explosion they did actually revert the site. Donald exploded again and then, a few days later, he made the full second half of payment.
Its not the customer's property, you could DMCA takedown notice the customer's host if you don't have access to the site.
In regards to hired labor undoing work done, I've done that with a hand from my local sheriff here in Washington state. Theft of services and not paying for hardware installed is stealing, which just so happens to be a crime.
No, if the customer gave me authorized access, your damn straight I'm going to take down my work, and not via a DMCA as they would still have a full copy. If that were illegal under CFAA then bricking a computer using Computrace wouldn't be legal.
That being said, the CFAA is overly broad, but if something like this were to get taken to court it would almost certainly get thrown out unless its a kangaroo court.
Also, I don't involve the sheriff's office unless I feel there is likely to be significant pushback or threats when recovering said property. Involving them doesn't magically change the legal situation.
This depends entirely on the terms of their contract, which were not disclosed. There are myriad ways in which this would be entirely legal depending on phrasing around delivery and payment.
