Canned foie gras is generally ok -- not vacuum sealed in plastic, not in glass jars, but canned. The dogs certainly won't get excited about a can. The only time I ever had a problem was during a bird flu scare. I was going through customs around 8 pm and it wasn't possible to verify, with the Ag department in DC, that this particular lot had come from an uninfected area of France, so I surrendered the can.

Be sure the product doesn't have any pork in it -- good foie gras won't, only duck (or goose) and its fat plus a little salt, maybe preservative. Buy it in town -- sometimes the foie gras specialists have promotions this time of year but even the grocery stores have reasonable products, and the airport prices are high. Look for "foie gras entier" rather than "bloc de foie gras". Pack it in your checked bag so that it stays cool.

Customs and immigration are federal, so the California foie gras ban shouldn't matter.