In the movie Catch me if you can. Tom Hanks, as an FBI agent, is on a manhunt for DiCaprio, as a counterfeiter. As a non American I always assumed the Secret Service was the agency responsible for counterfeiters.
How come in Catch me if you can it is the FBI that is responsible for the counterfeiters (when DiCaprio gets caught, he gets to work at the FBI counterfeiters office).
Correct me if I'm wrong, but didn't he start out forging payroll checks? The Secret Service is concerned primarily with combating counterfeit currency - i.e. dollar, dollar bills, ya'll. Counterfeit checks would still be under the auspices of local law enforcement and, if they crossed state lines in the commission of their crimes, the FBI.
Either way, it was not long before Abignail, the character DiCaprio plays, was guilty of many, many other federal felonies, which would have put him on the FBI's radar, and in the Federal pecking order, the FBI is going to get first shot before Treasury.