To all, on this topic
It is clear to me from some searching that I did, that it is no longer the case that prices are fixed at the pump, in Utah. I looked for some evidence on the web that the prices ever were fixed but the search was very tough going, and I gave up.
You can believe my testimony or not, as you choose. If you choose to believe me, then you are left with my assertion that there were no shortages nor riots nor any dissatisfaction that I could discern in Utah during my visits there.
I think that Ps ideology-inspired pronouncement speaks for itself. The way to prove something is to try it out.