I'm not sure why you are being downvoted for this, unless you are being interpreted as snarky (whereas I interpret you as offering a noncommittal answer).
While it has not been settled in court yet, IIRC, the 5th amendment right against self-incrimination is the legal rationale used to argue against forced decryption [1].
[1] https://www.eff.org/deeplinks/2013/10/new-eff-amicus-brief-a...