Scott,
In Califrnia for sure and I do believe it to be federal law as well. All that is needed during the warranty period is a dated sales receipt from an authorized dealer.

There was a big to do seceral years back over the warranty card issue and companies backing out of warranty repairs, because the card had not been mailed in. Although I do not recall all the secifics, I am sure the feds passed a law that all is needed is a dated sales receipt.

That is why most of the time now you see things on the warranty card like.....free magazine, or keep you aware of updates, or free whatever.....for mailing the cards in.
Terry