In a precedent-setting decision for the environmental-justice movement, a federal judge last week blocked the opening of a cement additive plant in a poor black neighborhood in Camden, N.J. The New Jersey Department of Environmental Protection gave the go-ahead to the plant last October after determining that it would not exceed federal air-pollution limits. But Judge Stephen M. Orlofsky said that the department had violated permitting rules under Title VI of the federal Civil Rights Act. He gave the DEP 30 days to conduct a broader review based on the U.S. EPA’s environmental-justice guidelines, which are meant to prevent minority and poor communities from shouldering an unfair pollution burden. The judge’s decision could prove to be an embarrassment for U.S. EPA Administrator Christie Todd Whitman, who was governor of New Jersey when the plant was approved.