"The relationship created a clear potential for conflict," Innes wrote. "These types of communications would be the sort of communications the Supreme Court felt the public had the right of access to understand and evaluate the reasonableness of the public body's actions."
Corzine and Katz dated from 2002 to 2004 and exchanged e-mails during state worker contract talks that ran from late 2006 to early 2007.
New Jersey Republican Party chairman Tom Wilson filed suit to make the e-mails public, alleging the relationship could have tainted negotiations.
Wilson's attorney, Mark Sheridan, said the order requires Corzine to release at least 745 documents within about two weeks.
"We'll find out whether or not Jon Corzine was representing the best interests of the state of New Jersey or acting on the behest of Ms. Katz," Sheridan said.
The Democratic Corzine contends the e-mails are private under privileges afforded governors.
Katz, president of the largest state worker local, claims they are private because they were personal and involved confidential contract talks.
"The public has a right to know whether the relationship between the governor and Ms. Katz had any improper influence on the governor's paramount obligation to serve the interest of the citizens of New Jersey first," Innes wrote.
Sidney Lehmann, Katz's attorney, said they will appeal.
"We continue to believe that these e-mails, sent with the expectation of privacy, should rightfully remain private," he said. "We believe that the court's ruling is wrong. We will appeal it and continue to vigorously fight for the time-honored rights to confidentiality and privacy."