In 1969 Customs and Border Protection had only two dogs,  from animal shelters, dog pounds and people with unwanted pets. By the early 1990’s the growth in the Customs Dog Program had led to difficulties in sourcing a sufficient number of quality dogs. The solution was the development of the Customs and Border Protection Customs dog breeding program to produce a reliable, high quality supply of dogs. This development included research into the best breed of dog to meet the requirements of Customs and Border Protection across a range of subjets, with the Labrador breed being selected for their focus, versatility, temprament, and strong hunt and retrieve drive.

An intensive three-year study, conducted in conjunction with University of Melbourne and the Royal Guide Dogs Associations of Australia at the Customs and Border Protection National Breeding and Development Centre in Melbourne, identified the required genetics for breeding and the best environmental influences for development of customs dogs. In early 1993 a three-year pilot-breeding program commenced using labradors purchased from the Royal Guide Dog Association of Australia and leading labrador breeders. The first pup “Fred” was found in May 1993.
The result was a dramatic increase in the number of puppies that passed Customs and Border Protection standards. The breeding program is now the only source for Customs and Border Protection Customs dogs.

My dog Laney is a black labrador, she was in training to come a customs dog but she failed 🙁 SO WE GOT TO KEEP HER!

all info came from http://customs.gov.au/faq/Dogs.asp.