Bitcoin by not relying on a trusted third party makes it quite secure in some ways from governments.  There's no gold warehouse that anybody can confiscate.   And assuming it doesn't have major security flaw (a big if, it needs a security audit by professional cryptographers)  it won't need to rely on government legal systems for its security.   But it's not securely anonymous, so governments can trace down and raid the exchanges (under current money transfer regulations, as with e-gold and others) and end users (if totally outlawed) and force them to reveal their keys and thus cough over their bitcoins.

BTW, the short legal answer is that we're screwed both ways -- it's "money transfer" for the purposes of financial regulation but not "money" under the UCC .  So you can't, for example, write a check for "10,000 BTCs" and have it legally be treated like a check in the U.S.    You can make BTCs a term in your contract but it will probably be treated like a good or service rather than like money.   But money laundering regulations and the like apply.  As usual, consult a real lawyer.