First, all property is a government monopoly, unless you're one of those religious libertarians that believe God created rights in real and chattel property. But I meet lots of libertarians that reject the idea that adultery should be illegal, so maybe there's some other holy book they follow.

Second, the root of the CFAA charge wasn't intellectual property, but physical property: MIT's network. Libertarians certainly do recognize non-contractual violations of property rights, i.e. various incarnations of trespass.

The CFAA charges were dubious at best, and were only pursued because the copyright charges were looking pretty shaky. The prosecutor also tacked additional charges on when Aaron decided to exercise his civil rights. I do not know many libertarians who support that kind of abuse of prosecutor power.

The premise of the CFAA charge is entirely consistent with libertarian thinking: owners of private property, like computer networks, are entitled to exclude people from their use, or revoke a previously granted license of use, for any reason at all. This charge makes sense even if you don't believe in intellectual property: it doesn't matter what he was doing on the network, only that he had reasonable notice that his license to use it had been revoked when they banned his MAC, but then continued to use it, thus trespassing. That's "get off my lawn or I'll call the cops." That's as libertarian as it gets. If you're talking about classic libertarianism, prosecuting trespassers (I.e. Securing property rights) is one of the few legitimate functions of government.

Arguing that violation of property rights is justified by some greater social purpose is distinctly unlibertarian.

As for "abuse" of the process, that's orthogonal to libertarianism. Classic libertarians believe in limited government, but once the legitimate object of government is implicated, in this case protecting property rights, they do not have any tendency towards favoring more forgiving or lenient prosecution.

Banning a MAC from an open network isn't "get off my lawn or I'll call the cops", it's more like "quit taking all the potato chips; save some for others and come back later."

That's an utterly ridiculous characterization. Its an attempt to convey that someone is no longer welcome to use your property. Not only is it such that a reasonable person would take it to have that meaning, which is all that's required, but Aaron actually understood that he was no longer welcome to use the property because his subsequent accesses to the network were under disguise.

That might help your argument if that was the extent of the measures used to kick Aaron off of MIT's network...

Every Libertarian I've ever met believes in contract law, and that essentially ANY penalty can be attached to willful violations of contract.

Under a Libertarian regime, the whole thing would've been simpler, as no theory of justice or societal good would've been involved. It would've simply been JSTOR and MIT extracting whatever revenge they'd considered.

Its not just a breach of contract, because Aaron accessed the network again after his license had been revoked. That was a distinct violation in the nature of trespass, a property law concept.

Let me illustrate. Say you belong to a private club. The contract of membership allows you to use the clubhouse, as long as you don't bring any Hindu guests. Say one day you do. That's a breach of contract. Say you come back the next day. Since you've breached the contract, your license to use the house is revoked, and now its an infringement of property: trespass. Finally, lets say you punch the owner for being racist. Any classic libertarian will support prosecuting you under three legal theories: breach of contract, trespass, and battery (a tort). Classic libertarians don't reject any of these.