Google pulls up nothing public yet, but per communication to FAs and CSRs:
- If a customer is checking their bag, they must remove any lithium-ion batteries, including those that are part of the bags themselves (smart bags) prior to checking the bags.
- Once removed, these batteries can be transported in carry-on baggage.
- Bags with non-removable batteries are not allowed on any United or United Express flights, either as carry-on or checked baggage.
As an added precaution, during curbside, lobby or gate acceptance of baggage, customer service representatives and vendors will ask customers about the presence of lithium ion batteries or e-cigarettes.
(Bolding mine)
I can't think of any bags where this would be an issue, but hey, maybe you all can.