The Bush Administration sued the city of Oakland on Wednesday for declaring itself a nuclear-free zone, saying the ordinance violates exclusive federal authority over nuclear weapons and could force some federal installations to leave. Oakland's nuclear-free ordinance, approved by city voters last November, is one of the broadest in the country in restricting nuclear weapons-related activity. City Atty. Jayne Williams said she believed it was the first to be challenged by the federal government. Among other things, the ordinance forbids nuclear weapons work within the city in two years; bans city purchases from, or investments in, any "nuclear weapons maker" unless no reasonable alternatives exist, and requires advance notice before radioactive material is hauled through the city.