You are not participating in a federally or internationally regulated credit system.
Irrelevant.
holds no value in the real world beyond that which is put on it by the members of the community that use it.
Like gold.
Bitcoin is no further subject to federal regulation, law, or consumer protection than something like WoW gold.
Theft of virtual items has been successfully prosecuted all over the world.
See, I tend to care about what's actually true instead of going on a rambling spree. You should try it.
The only two courts in the world that have set any legal precedence in regards to virtual items or currencies holding real-world monetary value are the Dutch, and South Korean courts. Neither of which either of the two individuals involved are subject to the jurisdiction of.
Gold holds value in the real-world because it's a precious metal that is the backing of, or used to be the backing for, every currency on the planet that was created for an established economy. However, gold is not legal currency in the United States either, save for the state of Utah, which only recently passed legislation to identify it as legal tender.
The fact that neither party is participating in a recognized monetary system with binding laws, rules, and regulations is perfectly relevant to this situation. I urge you to show me where US federal courts (since this is international, and therefore a federal, not state matter) shows that virtual currencies of any form hold real-world value.
Likewise, I urge you to show any example that proves beyond a reasonable doubt that once you transfer ownership of an item (tangible or intangible) to another party, it is illegal for them to not give it back once demanded.
The point everyone (with the exception of a few) seems to be missing here is that phantomcircuit no longer owns them. BenDavis is an asshole for not sending them back, I will agree wholeheartedly, but he is not required to do so under any law. He owned the coins the second they were sent to him.
At most, you could try to claim that the Bitcoins he received were a good or service offered by the company (Intersango) and that the company requested a recall on the product. However, under US laws regarding consumer rights of recall and revocation, the consumer has the right to choose not to return a product that has been recalled.