He split, without looking it up, the Supremes sent the case back to the court of record. No defendent, no retrial, that's the extent of the precedent. It's weak. The lower court decision stands by reason of the defendents default.
That's basically it. The funny thing is that it gives more ammo to the pro-gun argument because it was more along the lines of "well, if you could prove this would be used by a militia, it would be ok." Which if extrapolated would mean that if you could bring it along and use it in a war, it's kosher.