Several puppies were seized in the raid.
Two other properties were also searched by police.
The operation took place on the Horsdean site in Brighton.
A Brighton & Hove City Council spokesman said: “Our trading standards team is leading an investigation into the illegal sale of a significant number of puppies in the city.
“This morning the team raided four premises on the Horsdean travellers site in Brighton as well as two other properties.
“During this operation they were supported by Sussex Police, the RSPCA and Animal Protection Services. The council is very grateful for their invaluable contributions.
“Four puppies and a bitch dog were taken as well as a number of electronic devices and documentation in relation to alleged offences under consumer protection legislation and breaching of animal welfare rules regarding dog breeding (Lucy’s Law).
“The investigation is continuing with a view to prosecuting anyone involved in this illegal and appalling trade.”
Source: Daily Mail