¿Aduanas?

I am curious bout this also. Last summer I returned on a Permanent Resident Visa; MCI-HOU-MEX-ZIH. My bags were checked thru to ZIH from MCI. In MEX I told my escort (I need a wheelchair escort)I needed to go thru Customs with my bags and then hen recheck them to board the AeroMex flight to ZIH. He looked at my tickets and baggage check ticket and said "No problem, the bags will be at ZIH and you go thru Customs and Immigration there". My bags were at ZIH and it was a late flight and the attendants waved he thru and said all the Customs and Immigration people had gone home. Go figure~