Intellectual Property (IP) is still defended by quite a few libertarians, but most of them either by default support it or they do not understand libertarian principles, e.g. body-ownership. It's very easy to see why IP is unjustifiable, despite the great amount of arguments for IP. It fails to be compatible with even the most basic libertarian rule: body-ownership. This is a short post (no where near exhaustive), but it deals away with IP swiftly.
As Hoppe, Kinsella, and I have shown, the body-ownership principle, i.e. "self"-ownership principle, is a priori true. It can only be denied with performative contradiction. The body-ownership principle implies the "objective link" rule; the rule is that for some specific person to own a specific scarce resource there must be an objective, "intersubjectively ascertainable" link between the two. For one's body it is the direct use of it, and for external scarce resources it is original appropriation.
There is no such objective link that ties an inventor in NYC to some other guy's identical machine in D.C. It is simply an arbitrary link. Rather, the inventor simply says he has property rights in all machines identical to the one he created. As such, IP fails to be compatible with the body-ownership principle, and is thus invalid.
I will eventually make a bigger post about IP.
I am Nick Sinard, an amateur economist and philosopher that follows in the rationalist tradition, specifically the Mises-Rothbard-Hoppe tradition. You can find my material at www.NickSinard.com and www.Facebook.com/TheNickSinard . I'll soon be putting up videos on YouTube about an array of topics, including "What is libertarianism?" You can find my YT channel at https://www.youtube.com/channel/UCFGA8_Ti30AbYiADPCo8Qgw