The majority opinion concluded that the federal government’s regulatory authority applies only to wetlands with a continuous surface connection to water bodies that are considered “traditional” water such as lakes, rivers, and streams, such that the wetlands are indistinguishable from those waters. 

This means that wetlands that are part of a hydrological ecosystem – including those that are connected directly via groundwater – but having no continuous surface connection to traditional waters, will no longer be regulated by the EPA and are now more vulnerable to pollution discharges and other threats that may lead to their destruction. This ruling also rejects the well-established practice of having federal protection for wetlands adjacent to regulated waters, that are only separated from these waters by man-made dikes or barriers, beach dunes, etc., and now requires wetlands to be physically adjoining instead.