IIRC, being able to make an archival copy is not a law, but is part of a Supreme Court decision (i.e. 'case law'). The DMCA was enacted after the Supreme Court decision, so I would assume that legally it would 'override' it. I'm definitely not a lawyer though so I have no clue if I'm right. Either way, I'm sure there will be a case at some point challenging this discrepancy to the Supreme Court and we'll see what they say at that point.