Ever heard of the dreaded time b*mbs.
Vendor spends time and money to develop a machine/process for a customer. The customer for whatever reason does not want to fulfill their end of the contractual payments, the time b*mbs goes off and shuts down the machine/process until which time the customer completes his contractual obligation.
I believe this would completely sidestep the legal avenues of recompense.
Crude but effective.
I have done that, but I had to take steps to ensure the customer *could*, if circumstances dictated it, "de-fuse" the bomb.
On a monthly basis, a new password (an eight digit number) was generated by the PLC, this had to be entered on the HMI to allow "major functions" within the application. Basically the machine wouldn't run in automatic without a password match. The intention was to charge a "fee" for each monthly password, partially deductible from outstanding invoices (I had a 20% "handling" fee).
At any time, a "master" password could be entered which would permanently enable all functions, disarming the "bomb" completely. The intention there was that the master password would only be revealed when I received full and final payment for all works carried out. The master password would be divulged for free.
They could, of course, have got another PLC guy to inspect the code in the PLC to overcome the password system, (it wasn't locked down for reasons I will state later), but that would be construed as "Reverse Engineering", which was explicitly disallowed in the contract. They were in full knowledge that I would pursue recompense through the courts if they did that.
Either way I figured I would get my money - somehow....
Now why did I not lock-down the password generation code ? Obviously if something drastic happened to me, such as going out of business, incapacitation, or even death, they would then be able to use the machine, by getting someone to "reverse engineer" the password code.
I started the ball rolling when the software was fully-functional, which happened to coincide with a password change, so that left them a month for "validation trials" before they would come knocking on my door for a new password. Thankfully, they were over-the-moon with the machine, (it was a refurb), delivering higher throughput, and better accuracy than ever before. I got paid just before the password expired, and told them the permanent "disarm" password.
