A political battle is brewing between the Port Authority, supported by Governors Cuomo and Christie, and the New York Police Department, supported by Mayor Bloomberg and Commissioner Ray Kelly. At its most elemental level, it’s a turf war. But it’s more than that, because the turf in question happens to be the World Trade Center site, hallowed ground for some, an inevitable terrorism target for others.

The Port Authority and the NYPD have an agreement that gives New York’s Finest authority over security at the site. But word has it that officials at the Port want to do away with that agreement and put Port Authority cops in charge.

Gov. Christie of New Jersey has been his usual blunt self. “Never, not on my watch, will there be any other police force who will patrol the new World Trade Center other than the Port Authority police,” Mr. Christie said recently—as he accepted the endorsement of the P.A. police union.

The Port Authority police do a fine job. But Mayor Bloomberg and Commissioner Kelly have it right: the NYPD ought to handle security at the World Trade Center. City cops have the training and the equipment needed to protect the site not just from ordinary criminals but from the terrorists who certainly will try to attack the Freedom Tower.

Since 9/11, the NYPD has become a critical component in the nation’s security grid. Mr. Kelly has overseen the development of counterintelligence and counterterrorism training to deal with the complex threats New York faces. That’s not to say that the Port Authority force is inadequate. It’s just that the NYPD is better suited—by far—for this sensitive task. It should be up to the NYPD to keep the site secure.