Just thinking...

How about "FlagCoins" - you can flag your coins ahead of time so that they can only be spent on certain items when you choose to do so.  Once flagged, the coin cannot be spent in any other way until you spend it on what you flagged it for.  Then the new owner of the coins can flag them in any way they choose.

For example, you flag one coin that can only be spent on a certain size and brand of running shoe sometime in the future.  Anyone who confiscates it will have to buy that particular type of running shoe with it.  Or maybe groceries at a certain store.  Or produce at a certain organic farm.  Not worth the time for a .gov agency that has confiscated your flagged coins to sift through them, make the purchases, and then try to re-sell the eggs, shoes, gas, and everything else.  In effect, the coins are useless to them but useful to you for purchasing the everyday items you use.

Another idea might be to put a timer on each coin.  Every 7 days, say, the coins are automatically transferred elsewhere (accessible by you) if they haven't already been spent by you.  This means that if .gov confiscates your coins it had better move them quickly because POOF, they are suddenly transferred back to you at another location.