There is a very inexpensive solution to the problem that folks in snow regions know about when they have metal roofs. They are roof snow guards that are installed on the roof and prevent the snow from sliding. They come in metal or plastic and are just screwed to the roof in a designated pattern. Google snow guards for metal roofs and you will find hundreds of hits. Ask your neighbor to install them on your side of the building or offer to buy them for the neighbor. That will cost you a whole lot less than an attorney and all your time perusing it.
Once again you are making stuff up. It is always interesting that you never link to the ordinance or code that you say exists. And what you posted here is not correct.
This is the CA code (and it is the plumbing code):
https://up.codes/viewer/california/c...rm-drainage#111101.2 Where Required
Roofs, paved areas, yards, courts, courtyards, vent shafts, light wells, or similar areas having rainwater, shall be drained into a separate storm sewer system, or into a combined sewer system where a separate storm sewer system is not available, or to some other place of disposal satisfactory to the Authority Having Jurisdiction. In the case of one- and two-family dwellings, storm water shall be permitted to be discharged on flat areas, such as streets or lawns, so long as the storm water shall flow away from the building and away from adjoining property, and shall not create a nuisance[.
And under common law, you can't change the natural flow of storm water from one property to another. In other words, the water on an uphill property will flow to a downhill property.
This thread is not about storm water runoff. It is about snow sliding off a roof. How do you equate that a snow melt is storm water runoff?

