The answer to this question will depend on whether you have an I-94 card (paper) or an I-94A card (paper, issued at the land border) or an electronic I-94 card (which may be printed from the CBP website following admission to the U.S.). By regulation, returning to the U.S. after a trip to Canada or Mexico of less than 30 days is possible using an expired visa stamp IF the traveler is in possession of a valid I-94 card.
If the traveler is in possession of a paper I-94/I-94A card, the rules have not changed – this document should be stapled into your passport and not turned in when departing the U.S. for Canada or Mexico.
If you have a “new” electronic I-94 card, CBP has stated that the record of admission would be in their database (and the admission stamp with relevant information would be in the passport) so a print out of the electronic I-94 card is not mandatory to travel pursuant to this rule, but that it would be a good practice for the traveler to print and carry the I-94 card with them anyway.
Please see our FAQ with detailed information about this Automatic Visa Revalidation process on our website at insert link as this process is not available to everyone.