Let's hope we never get to test this hypothetical, because it might even be easier to confiscate BTC - certainly to merely destroy BTC, and thus raise the value of your own. When a physical force comes knocking, it's going to be tricky to resist sharing a key - and unlike physical stores of value, digital trails of ownership might make it quite a lot trickier to deny ownership; it really depends on how much information that occupying force has.

Also, it's trivial to freeze BTC accounts too; that just means controlling the network - which in the even of a physical occupation is going to be obvious anyhow.

Then there's the fact that occupiers may be able to engage in a 50% attack (assuming occupation is large scale and impacts many miners) - and may well force usage of their fork of the chain, even in absence of a global 50% control, making the whole thing rather tricky to predict.

Let's hope it never comes to that, but I'm certainly not convinced BTC would be immune from a physically occupying force's influence. I bet it depends hugely on the details of that occupation.