Copyright infringement happens when someone makes an unauthorized copy of a work which is indeed copyrighted. This is a fact, regardless of whether or not the party who made the copy sells, gives it away for free, etc.

The owner of a copyrighted work only has control over authorized copies of the work until the time of the first sale of that particular item ("the distribution right"). After that item is first purchased, the copyright holder no longer has any say about how the item is further distributed.

For more details about this see http://www.bitlaw.com/copyright/scope.html

With regards to selling GLO memorabilia on ebay or thru other means, there is nothing legally wrong with that. The only time any group would have a claim is if some party were selling unauthorized copies - or if there was unauthorized (non licensed) use of the fraternities trademarked name/symbols. I bet that anyone could go to a greek store on the internet (offline as well) and purchase any items they want, with any organization's letters on them.

My guess would be that most of the older memorabilia being sold were obtained at estate auctions, etc.

Some people may feel that it is not ethical for people "in the know" to sell these types of items, but it is definitely not illegal to do so.