This is the direction places like the UK have gone in, yes. Can't decrypt something? Then we assume it is illegal content.
The whole point of this technique is that with sufficiently low information density the data is not recoverable unless you know what you're looking for, because it's indistinguishable from noise.
"I don't believe you, so now you're going to be in the locker for contempt of court until you provide law enforcement access to this critical evidence."
Then it is reasonable to assume that you can just show us these internet memes?
Again: the signal is below the noise floor. Unless you really know what to look for, you'll just find noise. Whoever seizes these files would have to at least know the specific method used, particularly if the content is also encrypted.
Take for an example JPEG as a vessel for steganographic content: the image is divided into 8x8 pixel chunks. If you encode just one bit of entropy in each chunk, a 320x240 image will yield 1200 bits, so 150 ASCII characters. Mangle it with a one-time pad for good measure so that it actually looks like noise. How did that noise get there? Well, it's lossy compression your honor.
There are so many ways to encode that one bit in such a large piece of information that authorities are better off drugging, bribing or torturing you or whoever was the recipient of that message than trying to decode it.
https://en.wikipedia.org/wiki/Export_of_cryptography_from_th...
"It's just math, you can't ban it" has never been true.