Well, its not the law yet, but the House of Representatives passed the Plain Language in Government Communications Act of 2008. Now we just need the Senate at GW to join up.
The basic idea is that all government documents will now include "language that the intended audience can readily understand and use because it is clear, concise, well-organized, and follows other best practices of plain language writing". Sounds like usability to me (and to Caroline Jarrett at Usability News - thanks for the pointer).
This is only half the battle too. Its one thing for the government to promise to make its documents user friendly. The next step is to require other people to make their contracts easy to understand and use (see my book chapter on how to do this). The lack of readable contracts is part of what got us into the credit card mess, subprime mortgage mess, health care insurance mess, and many others. We wouldn't need half as many lawyers if contracts were understandable. But of course, lawyers write the contracts, so . . . .
And for anyone who thinks that regulating contract language is anti-free market, think again. This is a strong libertarian idea. If companies had to make their contracts understandable to their intended customers, those customers could be freed to sign up for any kind of contract they want (except for the universal taboos like slavery etc). They would know what they are getting themselves into and be "allowed" to make that choice.
The reason we need regulation that actually limits behavior is because customers don't/can't understand the fine print. So we have to prevent companies from putting nasty stuff in that fine print. But if the customer understands all of the details and still wants to enter into the agreement, why not let them? This only works when we have understandability.
This new Act is a good first step. Go Congress Go !!!