Project opponents say the environmental review was flawed.

Minnesota regulators have urged the state Supreme Court to deny challenges by opponents of Enbridge Energy's proposed Line 3 oil pipeline replacement who say the project's environmental review was flawed.

The Public Utilities Commission told the Supreme Court Tuesday it believes the review was "adequate in all respects."

Enbridge wants to replace its existing Line 3 across northern Minnesota, which dates from the 1960s, because it's deteriorating and runs at only half its original capacity.

The Minnesota Court of Appeals upheld most of the environmental impact statement last month, but sent the case back to the PUC for further proceedings because the review did not address a possible spill in the Lake Superior watershed.

Environmental and tribal groups want the Supreme Court to back their challenges on other issues, too.