He said California's Fair Political Practices Commission, the state attorney general and local district attorneys are the appropriate entities to handle allegations such as those against Carona.
The case is "exactly the kind of area where the federal government ought to stay away," Cline said.
U.S. District Judge Andrew J. Guilford did not issue an immediate ruling.
Federal prosecutors contend Carona and others conspired to get him elected in 1998 so he could use the office to enrich them with bribes. Carona and others are accused of accepting tens of thousands of dollars in campaign donations and gifts, including Lake Tahoe vacations and a boat, in exchange for political favors.
Carona, who was head of the nation's fifth-largest sheriff's department, has pleaded not guilty to one count of conspiracy, four counts of mail fraud and two counts of witness tampering. He retired as sheriff in January.
Assistant U.S. Attorney Kenneth Julian responded that the charges were appropriate, noting that Carona failed to mention the gifts on disclosure forms he sent through the mail.
"If you get payments and then you lie about them, and then you take steps to benefit the payer," that's mail fraud, Julian said.