It doesn't seem constitutional to levy a 100% on any small group of people working at a private firm. Especially when that money is contractually obligated to them.
"American families shouldn't be forced to reward these professional financial failures with extravagant bonuses that could buy fancy cars and yachts," Israel said in a statement. "AIG may not like it, but since they had to come to the federal government for help, the federal government now has a say in how they spend taxpayer money."
It just doesn't seem like the kind of thing that could pass the Supreme Court. What would keep the Congress from passing a 100% tax on Exxon or someone in order to run them out of business? What if they wanted to squelch unpopular speech by levying a 100% tax on a radio station or a TV network? This seems like a slippery slope.