All references are based on the 2020 edition of the NEC.
Double Duty Connector
Using the clamp screw of an NM cable connector for terminating the equipment grounding conductor (EGC) is a violation of Sec. 250.8. EGCs, grounding electrode conductors (GECs), and bonding jumpers are permitted to be connected by listed pressure connectors such as twist-on wire connectors, terminal bars, pressure connectors listed for grounding and bonding, exothermic welding, machine screw fasteners that engage at least two threads or are secured with a nut, thread-forming machine screws engaging at least two threads into the enclosure, connections made as part of a listed assembly, or other listed means. Using an NM cable connector for connecting an EGC is not one of the eight permitted means specified in Sec. 250.8. This installation probably does not comply with Sec. 250.12 either because the paint was not scraped off the surface of the enclosure to ensure electrical continuity between the connector and enclosure. The NM cable connector may be listed for securing NM cables, but I’m sure it is not listed for grounding and bonding purposes. As such, this would be a violation of Sec. 110.3(B) as well.
Corrosion Catastrophe
I spotted this installation in the basement of a commercial business located in an old building having a fieldstone foundation. This type of foundation can be notorious for allowing water seepage through the foundation walls. That was certainly the case for this building. The basement was extremely humid and damp with moisture dripping from many surfaces. I think this basement would certainly fit into the Art. 100 definition of a damp location. All the moisture in this basement has certainly taken its toll on the metal wiring methods installed here. Section 300.6 requires raceways, cable armor, boxes, cabinets, fittings, supports, support hardware, and other materials and equipment to be made of materials suitable for the conditions. Perhaps some better choices could have been made here. Sec. 376.12(2) prohibits metal wireways from being used where subjected to severely corrosive environments. Installing a nonmetallic wireway might have been the better option. Section 320.12(2) prohibits AC cable from being used in damp or wet locations. Section 334.12(B)(4) prohibits NM cable from being used in wet or damp locations. The NM cables and other cables secured with cable ties to the rusted EMT raceway do not comply with the provisions specified in Sec. 300.11(C).
