In 2013. He pled guilty to wire fraud in 2012. Can FinCEN/IRS retroactively determine something (like tradable skins in a game) is property and prosecute people over it?

> In 2013. He pled guilty to wire fraud in 2012.

He pled guilty on Nov 4 2022, the wire fraud occurred in 2012.

That's why I emphasized always. The laws and precedents saying that anything that quacks like property is taxable property are decades old so they predate Bitcoin. In 2013 the government just said "Remember these laws from decades ago? No? They apply to you."

If it's not property, what is it?

If you can own it, it is property; if people are paying money, or exchanging goods or services with value, for it, it is valuable property. Enforcement agencies publishing a ruling or opinion as go what kind of property it is (and isn’t) isn’t what makes it property.

If you find a bug in a multiplayer FPS (let's say d-pad rocking to allow you to wall-climb or something) that gives you a competitive advantage, and you use that competitive advantage to best players and win their assets in combat, can you be arrested for fraud/theft?

If you systematically use it at large scale and make enough money to be worth prosecuting yes. People have been arrested for writing code to play 100000 FIFA games a day in order to get in game coins to sell (https://www.theregister.com/2016/11/14/ea_hackers_charged_fo...). The wire fraud statute is incredibly vague and can be used to justify almost any prosecution. Some others: using fake names on accounts used for botting Ticketmaster is wire fraud, a wire transfer made as part of a commercial bribery scheme is wire fraud even though commercial bribery is legal federally.