Congress wouldn't dare pass it, and the President wouldn't dare sign it. The law you suggest would also be impossible to implement without violence on a grand scale. It would be the persecution of the Kulaks translated into the Information Age. The modern left just doesn't have the guts to try. The USA is much diminished from its glory days, but it still isn't Argentina.
If the stock market crashes once again, and American workers lose 65% of their 401-(k)’s, I could imagine a lot of them would be more than interested in the prospect of a guaranteed return of 3-5% with no risk to principal.
Well this administration has no fear of congress or the people....so yes he'd dare and would. This administration is not going to let the 401k money lay around without telling the American people they have a plan to invest it on their some whacky purposal to ease it out of from under the people sitting on it. It's pretty much a given IMO...as rules and regulations...congress and the people... are not this administrations concern.
Just like when Paulson went before Congress on bended knee saying the sky was falling....you can expect we'll hear that without using the 401k the people will be responsible for the downfall of the economic markets.