While generally a fan of the "free market", it doesn't seem like some level of minimal rationing is totally unreasonable for calibers that are hard to keep in stock (no I don't support the one box limit ). I was in a Walmart during the middle of the scare and saw a guy talk a new clerk into allowing him to buy a couple CASES worth of 45 that had just been put out because the "maximum 6" limit sign had magically disappeared. This was with multiple others of us present who just wanted a couple boxes for actual shooting. He was obviously going to resale it, and actually had the audacity to offer some to us after he had paid
If a retailer wants to impose a limit, they can.
If they don't want to, well, then there won't be one.
You can give feedback to retailers and tell them you like, appreciate, and support purchase limits, and you can go out of your way to purchase from retailers that have limits, both now and whenever the market returns, continue to purchase from them, to show your support where it counts.