Earlier I'd written a piece on the limits and forces of software (sorry, you'll have to log in to the Handbook to see that page). There's a recent thread on Slashdot that's a classic example of a legal force: a proposal has been made in Congress to extend Daylight Savings Time.
I would imagine that our federal representatives have not give any consideration to the vast amounts of legacy software, both,embedded (i.e. in a ROM on your DVD player) and patchable (e.g. Windows) that will be rendered incorrect.