ELI5: How can cannabis oil be illegal but CBD oil be legal?

My little sibling keeps buying CBD oil with THC (or something?) in it from grocery stores. But doesn't cannabis oil also have THC in it? Shouldn't the CBD oil be illegal too? Does anyone know anything about this?<br><br>Edit: Thank you guys. <br><br>It's weird that a drug that's legal in so many states in the us is still technically illegal federally, and illegal in other countries. And the laws around CBD seem to be complicated, but it seems like most laws about CBD vs marijuana are about the amount of THC in there. Apparently the CBD oil bought in stores usually has <3% THC? But idk, maybe that changes in different states/countries as well. <br><br>I couldn't find any info about hemp, so maybe that's just the same thing as CBD. <br><br>But it makes sense that just because it's legal in some places doesn't mean that it's legal *everywhere* or that it should be legal everywhere, right? But it also makes sense that if it's legal in some places then it should be legal everywhere, especially if it's helping people. It's so complicated. Thank you guys.