In March, a woman named Cara Schaffer contacted the Student/Farmworker Alliance, saying she was a student at Broward Community College. Her eagerness aroused suspicions, but she was allowed to join two of the group’s planning sessions. Internet searches by the alliance revealed that she was not a college student.

Image Credit... Francesco Bongiorni

Ms. Schaffer is the 25-year-old owner of a private security firm. Her company, Diplomatic Tactical Services, seems like the kind of security firm you’d find in one of Carl Hiaasen’s crime thrillers. Last year Ms. Schaffer was denied a private investigator’s license; she had failed to supply the Florida licensing division with proof of “lawfully gained, verifiable experience or training.” Even more unsettling, one of her former subcontractors, Guillermo Zarabozo, is now facing murder charges in United States District Court in Miami for his role in allegedly executing four crew members of a charter fishing boat, then dumping their bodies at sea.

In an interview, a Burger King executive told me that the company had worked with Diplomatic Tactical Services for years on “security-related matters” and had used it to obtain information about the Student/Farmworker Alliance’s plans  in order to prevent acts of violence. “It is both the corporation’s right and duty,” a company spokesman later wrote in an e-mail message to me, “to protect its employees and assets from potential harm.”

But the Student/Farmworker Alliance and the Coalition of Immokalee Workers are not dangerous, extremist groups. Both are pacifist, mainstream nonprofits inspired by the work of the Rev. Dr. Martin Luther King Jr. The coalition is supported by the Robert F. Kennedy Memorial Foundation, the Presbyterian Church (U.S.A.) and Pax Christi, the Catholic peace movement.

The Bill of Rights was adopted to protect Americans from the abusive power of their government. I’ve come to believe that we now need a similar set of restrictions to defend against irresponsible corporate power. Today companies like Wal-Mart and ExxonMobil have annual revenues larger than the entire budgets of some states, and they employ former agents from the F.B.I., the C.I.A. and the Secret Service to do security work. Unlike government agencies, whose surveillance activities are supposed to be conducted according to strict guidelines and court orders, these private firms operate with a remarkable degree of freedom. At the moment, federal laws against the practice of “pretexting”  using a false identity to obtain personal information  apply only to financial and telephone records.