I'm not a huge Geohot fan, and I am very anti-drugs (even pot) but it seems like this is pretty ridiculous.
Whether you agree with Medical Marijuana or not, the bottom line is the guy had the paperwork for it, even from out of state. He was travelling through Texas, as opposed to taking up residence or spending a prolonged amount of time there. Believe it or not there are laws to protect people from things like this, given that even outside of MJ there are all kinds of laws that vary from state to state about medication, which limit what the law enforcement can do to someone who is just "passing through", mostly oriented at painkillers though given that they are an abused substance and states have greatly varied laws dealing with them, but nobody thinks it's a good idea that someon in extreme pain should be arrested or have their pills confiscated for just passing through somewhere with differant laws (even if this can be abused by dealers).
My first thoughts here are that Geohotz is BSing about the legitimacy of his Medical Marijuana liscence and that's part of the story that isn't making it out yet, basically the cops checked it, and he is going down for lying about it. My second thought is that if he got it approved and wasn't hanging out in the area for a prolonged period when he was stopped, is that a Sheriff is about to lose his job, and that town is probably going to wind up having some major budget issues very quickly when they get the crap sued out of them.
It's not an area of law I know a lot about, but I do remember reading about some similar seeming cases with people being arrested for possession of prescription painkillers like Oxycotin, in states that tried to pass policies saying that they wouldn't accept prescriptions written from doctors out of state (due to the requirements they put on their doctors to prevent quacks from selling prescriptions for them to junkies) as justifying possession... and that didn't hold up when properly challenged. As I remember it, you can only challenge a prescription and presumably a liscence like that, if it's being used by someone who is a resident of the state in question. Basically you couldn't get your prescription for Oxy from a quack in California and use it in Texas (for example) or use it to justify possession, but someone playing tourist in Texas who brings their drugs with them can't be arrested for having them. As I understand things if Geohotz bought his MJ in Texas using the out of state liscence that would be a problem... but that would reflect more on the dealer/vendor if they accepted the liscence than on him. In the case of prescription drugs (ie not MJ) I believe medical professionals have ways around the laws as well, though they have to register what they are doing, so basically if some guy from California legitimatly loses a much needed medication like Painkillers for an obvious condition (burn damage or something), a doctor or pharmacy can oftentimes find ways to overrule the law as a medical emergency.
I'm rambling, but I think this is going to be a giant face off between two jerks ... a Jerk Off! (lol, sorry, I couldn't resist). A jerky texan sheriff, against a jerky west coast hacker. Personally I'll be very surprised if when the smoke clears Geohotz doesn't win, and probably even benefit from this.... assuming there isn't more to the story like a false liscence, him hanging out in the town for three weeks (or whatever the requirement is) or scoring his weed there in Texas.