Opponents of an Obama administration rule aimed at protecting small streams and wetlands from development and pollution now know which courts should be hearing their lawsuits.

The Supreme Court ruled unanimously Monday that litigation over the rule should begin in the lowest level of federal courts, not in the federal courts of appeal. The rule has never taken effect because of lawsuits and is now under review by President Donald Trump's administration.

The 2015 rule sought to settle a debate over which waterways are covered under the Clean Water Act. The debate has dragged on for years and remained murky despite two Supreme Court rulings.

President Barack Obama's administration redefined "waters of the United States" protected under the act to include smaller creeks and wetlands.