At border crossings they can deny you entry into the country if you refuse to allow your devices to be searched. Even if you're a US citizen re-entering the US, you will be denied entry if you don't comply. So while that can't force you they have pretty strong power of coercion, to the point where you're forced for all practical purposes.
Unfortunately this is true, border crossings are a special case and I'm still not sure what the best approach is for that. I imagine you would have to mail your device to the destination before you cross or just leave it at home. Alternatively, store the encrypted data in the cloud, download it at the destination, then wipe it from the device when you're done.