Effective June 1, 2009, a passport, passport, SENTRI pass, "secure"/approved DL (a Calif. DL is not an approved DL), or other approved ID is required to re-enter the US.  A birth certificate and DL are no longer accepted ID for re-entry.

Normally customs sends people with non-compliant ID to secondary. There they receive a lecture and a pamphlet listing approved ID. After secondary verifies the ID the person is allow to enter the US.

Some agents are saying that in time there will be a ($300.00) fine for entering the US with non-compliant ID.  But nobody knows for sure what the future holds.