The Mackinac Straits Corridor Authority was told Oct. 17 that the Michigan Supreme Court has granted leave to appeal most challenges to the Michigan Public Service Commission's order that authorized Enbridge Energy's replacement segment of Line 5.

"On September 19, the Supreme Court of Michigan entered orders granting the majority of those applications for leave to appeal," Devin Sullivan, the special assistant attorney general representing the authority, told the board. He said appellants must now file briefs, with appellant briefs due on Nov. 14, 2025; appellees' briefs will be due 35 days after that filing, and appellant reply briefs will be due 21 days after appellees file. Amicus briefs will be due at the same time as reply briefs, he said.

The Supreme Court consolidated several applications and directed focused briefing on two core questions: whether the Court of Appeals applied a deferential standard of review rather than deciding de novo whether the proposed conduct will "pollute, impair or destroy" air, water or the state's other natural resources under the Michigan Environmental Protection Act; and whether the MPSC properly limited the scope of evidence considered in its MPSC determinations, including whether the commission erred in excluding evidence about the history and risk of oil spills along Line 5's entire length. Sullivan also said the court granted a separate application filed by For Love of Water and asked parties to brief whether the common-law public trust doctrine requires the MPSC to consider public-trust obligations.

Sullivan said the court specifically invited amicus briefs from the environmental law and real property law sections of the State Bar of Michigan.

Why it matters: The Supreme Court's decision to hear the appeals preserves a legal path that could alter or delay regulatory approvals the project currently relies on. The court-level briefing schedule sets earned deadlines for the parties and defines the issues the justices will consider.

What happens next: Appellant briefs are due Nov. 14; the authority and project partners will monitor filings and the court docket for further scheduling. The board received this legal update for information and did not take action on the appeals at the Oct. 17 meeting.

Provenance: Transcript briefing began at 00:02:55 (Devin Sullivan) and concluded at 00:05:17 (Sullivan).

Speakers: [
{"name":"Devin Sullivan","role_title":"Special Assistant Attorney General","affiliation_type":"government","affiliation_name":"State of Michigan","first_reference":{"timecode":"00:02:55","transcript_line_range":[1,8]}}
]

Authorities: [
{"type":"court_case","name":"Orders of the Supreme Court of Michigan granting leave to appeal (Sept. 19, 2025)","referenced_by":["line5-supreme-court-appeals-2025-10-17"]},
{"type":"statute","name":"Michigan Environmental Protection Act","referenced_by":["line5-supreme-court-appeals-2025-10-17"]},
{"type":"other","name":"Michigan Public Service Commission order authorizing replacement segment of Line 5","referenced_by":["line5-supreme-court-appeals-2025-10-17"]},
{"type":"other","name":"State Bar of Michigan (environmental law and real property law sections) invited as potential amici","referenced_by":["line5-supreme-court-appeals-2025-10-17"]}
]

Topics: [
{"name":"pipeline_permitting","justification":"Article covers court appeals and regulatory review of Line 5 permitting decisions.","scoring":{"topic_relevance":1.00,"depth_score":0.80,"opinionatedness":0.00,"controversy":0.85,"civic_salience":0.90,"impactfulness":0.80,"geo_relevance":1.00}}
]

Provenance_segments: [
{"block_id":"175.79","local_start":0,"local_end":1234,"evidence_excerpt":"Thank you, mister chairman. As we've discussed at prior meetings, there are a number of pending appeals from the Michigan Public Service Commission's order that granted Enbridge's application to construct a replacement segment of Line 5 within the tunnel...","tc_start":"00:02:55","tc_end":"00:05:17","reason_code":"topicintro"}
]