Can a seller who has a gun permit legally sell a firearm to an individual who does not own a gun permit?

With new executive gun laws being a hot topic under the Biden administration, I had a question that I cannot find the answer to anywhere. 

I understand that in many states, it is legal for an individual to sell a firearm to another individual without personally conducting a background check or going though a licensed gun dealer (FFL). I also understand many states do not require a gun permit whatsoever to buy a handgun. 

However, my specific question is whether or not it is legal to sell a firearm to someone who does not own a LLC or gun permit, especially in those states which do require you to have gun permit to own a handgun?

If this is illegal, and only those with a gun permit can purchase a firearm from individuals, then it would make sense, because you need a background check in order to receive a gun permit in the first place, and so to some degree a background check IS being done. However, if it is legal, then these new laws would make a little more sense to me, since no background check has been ever conducted on the individual purchasing the firearm. 

Keep in mind, I understand these private sales happen anyways, illegally or legally, but I would like to specifically know "can a seller with a gun permit sell to a private individual who does not have a gun permit?".