Back in the day, in-line fuses at the poles. As to 'rules', it was what it was. I will look to see if there are any code issues.
We had fuse blocks at the pole tops to fuse each fixture, or to fuse 2 of a 4 group setup. 1000 watt HPS/MH in strip malls & shop ctrs. It avoided wiping out the circuit by a bad ballast.