The Securities and Exchange Commission has not yet decided whether broker-dealers should be given a fiduciary responsibility. But according to three of the nation’s leading authorities on fiduciary law, the courts and arbitrators have already said the answer is yes -- sometimes.

“If you are running a compliance operation for a big broker-dealer, you should expect your registered reps would be viewed as fiduciaries,” said Mercer Bullard, a professor at the University of Mississippi School of Law.

“The most common claim brought in arbitration against broker-dealers by investors is breach of fiduciary responsibility,” he said.

Determining what standards arbitrators use in applying a fiduciary standard to broker-dealers is a problem since arbitrators are not required to disclose the justifications for their decisions, though sometimes they do, Bullard added.

Arthur Laby, a law professor at Rutgers University, said that judges and arbitrators decide these cases based on the facts. But generally, the more discretion a broker has with customer funds, and the greater a broker's financial expertise is compared with a customer's, the more likely a broker-dealer will be found to owe a fiduciary responsibility to that customer.

Usually, people see the fiduciary responsibility as something reserved to major financial relationships with advisors, lawyers and other professionals. But the duty is also prevalent in simple, mundane transactions, said Boston University law professor Tamar Frankel.

For example, a parking garage attendant has a fiduciary responsibility when a driver hands over the keys, Frankel said. Giving access to the car is not carte blanche approval to do anything the attendant pleases with it.

In fact, one of the earliest findings on fiduciary duties concerned a seamstress given cloth by a customer to make a dress. Possession of the cloth, like possession of the car keys, carries with it a duty, Frankel said.

Broker/dealers must not only not misuse client money, they must also keep clients from making crazy mistakes, she added.