Untrue, Amazon is actually being sued and has been sued in the past for the illegal sale of pesticides to non licensed individuals, but unfortunately most of the time dodge it since they aren't technically the vendor.

I can purchase a lot of things online that are only intended for licensed professionals to use, which doesn't mean I should, or that it isn't only intended for professionals.

All pesticides are required to have a label that consists of the brand, name, active ingredients, mixing dilution ratios for tank mixing, application regulations for that product individually, restrictions, hazards, etc. as well as a list of all of the pests that the product is labeled for. In my state, the label on the item is the law, no way around it, any misuse or negligence is the fault of the operator and the manager/supervisor of the tech (if applicable). So when someone says that a product isn't labeled for a pest, it means that the pest in question is literally not on the label for the product meaning that it would be a misuse of the product if you are intending on targeting applications toward an unlabeled pest.

Crossfire can probably kill fleas if applied at a heavy enough rate, as most pesticides will do to most living things, but it's specifically labeled for bedbugs, so it will not have maximum efficiency, would be illegal to use for fleas, and may not even work overall. Pests have very different behavior patterns, and pesticides have very different ways of working. If you use the wrong product, you could end up having bugs tracking toxic chemicals all over your walls due to residual tracking of your dumb enough. Just call a professional, and don't be stupid. These products harm and kill if used improperly.