Attorneys argued over state and federal powers for more than four hours Friday on an effort by 13 states to block a new rule that gives federal authorities jurisdiction over some state waters.
The states, led by North Dakota, argue that the rules from the EPA and the Army Corps of Engineers illegally expand those agencies' powers under the federal Clean Water Act.
The law goes into effect next week. The states want the judge to order an injunction to suspend the new rules, which they say are causing confusion and anxiety.
An EPA attorney said during Friday afternoon's hearing that the rule clearly defines affected areas.
The other states joining the lawsuit are Alaska, Arizona, Arkansas, Colorado, Idaho, Missouri, Montana, Nebraska, New Mexico, Nevada, South Dakota and Wyoming.