It can be. We do have some problems with love potions, although they're not technically illegal. It's more that there have been people who have used the effects of love potions to cause the person they've given it to, to do illegal activities on their behalf. It gets complicated.
There is more and more Muggle influence, though, and there have been instances where the drugs that have been brought in have been enhanced by magic. Which, by the way, is definitely illegal.