Rule 21.5, d, (4) says: (emboldening is mine)
"Safety chains must be attached to either side of the tongue or connecting apparatus of the towed vehicle, equidistant forward and aft of the hitch or connector. They shall not be directly welded to the towed vehicle, but rather shall be connected by means of bolts, pins, or other secure connecting methods, that meet necessary strength requirements."
I re-did the safety chains on a small trailer that I annually take through their Panhandle, just to meet the requirements. Besides, it only had one chain to begin with. Most states require two, and of equal length, so I don't know what this "new thing", mentioned above, is all about.
Grade 8 bolts, washers, and nuts, both sides.
Duplicated it on our Flagstaff, too.