Nice solution! Google, can we get that on Android by default to reach the masses? Apple... you too: you built a reputation for protecting privacy.
While there's always https://xkcd.com/538/ there are not currently quantum computers that can factor 4k RSA keys, so the court can order whatever it wants, unless they have a way past that (which may involve variations of xkcd 538), they ain't getting shit out of a properly configured digital safe. (construction of said safe is left as an exercise to the reader.)
For the relative handful who are custodians of that sort of data, history suggests a smaller minority than they'd like to admit have a readily achievable breaking point. The true believers who are left then are a minority that's hardly impossible to track and subvert through attacks that don't involve decryption on a device.
The point of that XKCD wasn't to be THE SINGULAR EXAMPLE, it's sort of a Zen Koan for people who only think in terms of technical risks and solutions.