Yeah definitely more difficult, but it depends on the storage mechanism. But I suppose even if you simply had a private key hidden in some random folder or written down somewhere (there are more secure ways - one is breaking a key into multiple parts and spreading to separate people), it would be hard to locate or identify.
"Break it or go to jail" is already established law that pre-dates computers ("open this combination safe or go to jail"), but courts have generally held that this law also applies to encryption keys.
I suppose the bitcoin ethos of a decentralized network - with no single vulnerable point of attack - breaks down once you consider that until you can buy groceries, pay rent, and just generally use the currency everywhere, there's always the last point of vulnerability: wherever you convert it to "actual" money.
For a non-governmental currency that hasn't yet had its 5th birthday, I think bitcoin is doing decently well in terms of merchant acceptance. My personal opinion is that broad merchant acceptance will only come after it is widely used for investment/asset protection (if ever, of course). One indication for this idea is the magnitude by which forex volumes dwarf actual GDP. But it's all speculation :)
Actually seizing the Bitcoins would be very difficult, but there is (AFAIK) nothing stopping the Courts ordering a person not to deal with or dispose of the Bitcoins (or else be in contempt of court).