From your post it is obvious you are not an electrician, so why were you changing a light in a commercial building? It is also obvious that the original installer was not an electrician either. Do you see a pattern here? Maybe he should get a pretend lawyer to pursue action against the builder. Of course the result will be about the same as he has gotten so far by not using professionals.

As groundrod said, if you are not a licensed electrician, you have no business doing work in a commercial building. This is one area where cutting costs can be detrimental down the road. From what you describe, whoever installed the original wiring was also not a licensed electrician, or a very poor excuse for one. There's a saying - just because you put two wires together and the light comes on, does NOT mean it was done right. Get a professional in there to correct this, and any other issues.

Now that the flames and lectures have subsided I would like to add a bit more information
in hopes of getting some useful discussion about this situation.

Disturbed by the wiring mentioned above, I discussed
the situation with an uninvolved Licensed Electrician who opined that the fixture wiring
would have been OK if they had marked the green wire white to show it as a neutral.
Is there any support for that opinion here on this forum?

I have a serious concern over the compromised ground system that was discovered
and wonder what else may be improperly wired in the building.
I recommended that the owner advise the GC of the wiring problem
that was uncovered and ask that he (the GC) engage a competent but
uninvolved Electrical Inspector to evaluate the buildings' electrical system- with particular attention to the integrity of the ground system.

Does this seem reasonable as a first step and should anything else be added to the recommendation?

"Disturbed by the wiring mentioned above, I discussed
the situation with an uninvolved Licensed Electrician who opined that the fixture wiring
would have been OK if they had marked the green wire white to show it as a neutral.
Is there any support for that opinion here on this forum? "

if that's true, the "electrician" is an idiot and needs his licensed pulled.

Ground is a safety, it is not used in the circuit till something fails.

Are these on/off switches or 3way?

Are there two switches?

Black at the switch and white painted black indicates a switch loop. You cannot have both wires from the switch go to two different fixtures, one has to be the infeed power and the other will go to the fixture. Check the first fixture again for a white painted black.

Green is a ground wire. It can not by code be remarked white for use as a neutral.

Why ask for comments if you really don't want any? What you described is a very dangerous situation and should be repaired immediately by a licensed professional. To answer your questions directly; No there is no legal justification. It is highly illegal and potentially lethal to use a ground wire as a substitute for a grounded conductor. As to how the owner should proceed; he should increase his fire and liability insurance before doing anything else, because you have posted publicly the situation and he is aware, his liability has increased dramatically. There are attorneys that are just waiting to find out someone was injured or died from this situation. I also don't know why you take the simple truth as flames. I have no dog in this fight, but your laissez-faire attitude could end in someones injury or worse, and at that point you may also be liable to some degree.

Okay. I have no idea what in my post constitutes an "illegal string" but I'll be darned if I'm going to play some sadistic web designer's games.

A screenshot of my post:

{{!gwi}}

Okay, let's see your string parser filter a jpeg.

Thanks to all for the input.
Pharkus- Thanks for your input especially- I have no intention to fix it- but the fix you suggested would certainly eliminate the immediate problem.

My concern is about the hundreds of other parts of the system- some of which may have been done improperly as well- and which could be more dangerous. On the strength of this one example the day after this was discovered I strongly advised the owner to get the whole building inspected and repaired as necessary.

I apologize for misusing the handy term "bx"- it is of course MC. Showing my age I guess.

And Hexus- no he is not an idiot- just wrong this time. We usually discuss such issues thoroughly and come to a conclusion where he is right most of the time. But this time we didnt get to talk about it together- his comment was made to a third party and didnt get massaged by thorough discussion.