I haven't studied this law in detail, but it expect it is worded to avoid precisely this sort of manoeuvre, because the implication is quite clear - you have no right to privacy. If necessary they'd just confiscate your device and detain you on suspicion of perverting the course of justice etc, etc. they can hold you for 3 months for refusing to answer any questions they ask, including questions on your encryption scheme and how they can defeat it. They can also image all your hardware for future decryption, compromise it before returning it, etc.

I think the safer solution is not to travel with hardware you intend to use again.