Items or merchandise restricted by Mexican customs are considered prohibited and subject to authorization from the authorities. The list of items restricted by Mexican Customs can be found at the following address: http://www.sunat.gob.pe/orientacionaduanera/mercanciasrestringidas/index.html
Also, Mexican law limits entry to some products that because of their manufacturing can not be identified or checked upon arriving at the border since they do not have the necessary facilities. Their access is limited to some borders.