One of the problems with outlawing encryption is that it takes nothing to prove the crime, and therefore it is impossible to prove one's innocence.
Would it be possible to outlaw the possession or transfer of data that appears random? Nearly all data is random data, and nearly all processes randomize data. All data could be "proven" to contain information under at least one encryption scheme. It is the ultimate guilty until proven innocent argument.
If your credit card were erased with a magnet, could you now be prosecuted for the possession of encrypted data, because it could be proven that using a certain one-time pad it could be transformed into something meaningful to humans?
It doesn't end there. All things could be interpreted as information. We would have to start explaining the arrangement of books on a shelf, of spices in a rack, colours of stitching in clothing. If encryption were illegal, we would all be guilty all the time.
Fine, some would argue that random data isn't proof of guilt. What about the means of encryption? Now all random data are one-time pad keys. Prepare to rot in jail.