Is it legal to openly weld on the side of a road?

Throughout my career, I’ve been involved in industrial construction; chemical, mining, power, etc. The sites are always away from the public access. Each site has their own rules, but the safety principles surrounding welding are pretty consistent. Set up a weld barrier whenever possible. If you’re walking around an active welder, shield your eyes. Lastly, unless you’re wearing a weld mask, never ever look directly at the arc.

I take a busy major highway to work, which has been undergoing work for about 1 year now. On my way in today, I saw a worker welding right on the shoulder, about 5-7 feet from traffic, in a wide, open area. He was wearing a mask, but there was no barrier. Just an open arc.

Hundreds of 4000 lbs cars @ 60 mph, mostly driven by people who may be distracted or disoriented by the arc.

Was an rule or law broken?