Not at all. You're thinking of technical workarounds to the law -- which geeks often do, and which is generally not correct.
See, the two videos posted to YouTube aren't gibberish. They aren't raw materials. By using one to decrypt the other, you're not transforming them in the same way you're performing a transformation when you Photoshop a picture or mix chemicals together to make a bomb. You started with a video, encrypted it, converted it into an odd visual encoding, and posted the result to YouTube. Even though the result can separately be interpreted as a "gibberish video", it's history makes it clear that it's not, and through that history it retains its essence as a copy of the original video. Likewise, you cannot claim that a copy of the video on your hard drive is just a bunch of bits on disk, and you can't claim that a copy of the video on a VHS cassette is just magnetized tape.
The properties of encryption actually make it easy to prove that if the two videos can be combined to produce the "illicit" video, then it must have been the illicit video in the first place. The probability of producing anything intelligible (or even with a valid format) from a ciphertext and a key that don't go together is impossibly small. If you combine a ciphertext and a key and get something intelligible out, it must be the case (statistically) that they in fact go together and that the ciphertext was produced using that plaintext and key.