A long-running lawsuit challenging Minneapolis' 2040 Comprehensive Plan is likely to continue, after the city on Tuesday vowed to challenge a new ruling from the Minnesota Court of Appeals.

In a ruling Tuesday morning, the Minnesota Court of Appeals said Hennepin County District Judge Joseph Klein had relied upon the appropriate state law when he issued his ruling blocking the city from implementing its sweeping developmental plan. But it also sent the case back to Klein for further proceedings, saying he hadn't provided enough detail about how he arrived at his legal findings.

Later in the day, Minneapolis City Attorney Kristyn Anderson issued a statement saying the city plans to appeal to the Minnesota Supreme Court "and ask it to conclusively uphold the 2040 Plan."

The lawsuit challenging the 2040 Plan raised new legal questions as attorneys for the city and for three groups who sued debated how to interpret Minnesota's environmental protection laws. Recent phases have focused on a question of whether the city needed to conduct an environmental review on the entire plan or whether it could evaluate each project individually.

The 2040 Plan was quickly dubbed one of the most progressive in the nation when it passed in 2018. It eliminated single-family zoning, clearing the way for more duplexes and triplexes to be built in the city. It also allowed for the creation of "indoor villages" to increase the number of beds available for people experiencing homelessness and laid the foundation on which the city's transportation plan, zoning updates and a slew of other new ordinances were crafted.

Three groups who sued the city in 2018 — Smart Growth Minneapolis, the Audubon Chapter of Minneapolis and Minnesota Citizens for the Protection of Migratory Birds — argued that a full build-out of the 2040 Plan could cause environmental damage and the city should have conducted a review required under the Minnesota Environmental Rights Act (MERA).

Attorneys for the city, meanwhile, argued that it was unlikely the plan would reach its full scale anytime soon and that officials could instead review each project's impact individually.

After multiple rounds of legal arguments, the case ended up before the Minnesota Supreme Court, which sided with the environmental groups. The case then went back to Klein, who ruled that Minneapolis couldn't enforce the 2040 Plan unless it satisfied the requirements in MERA or "prevails in establishing an affirmative defense." He later agreed, though, to give the city a reprieve while it appealed his ruling.

The new opinion, written by Court of Appeals Judge Michelle Larkin, said it was appropriate for Klein to base his MERA analysis on the presumption of a full build-out of the 2040 Plan and "the city failed to raise a genuine issue of material fact" to rebut the environmental groups' claims.

In the Appeals Court, the city argued that Klein hadn't provided enough notice of the possible ruling — an argument Larkin wrote "does not persuade us" — and that his ruling lacked sufficient detail about how he arrived at his legal findings. Larkin wrote that the second argument was "persuasive," quoting the city's argument that said Klein's ruling didn't explain how reverting to an older developmental plan would have fewer environmental effects than implementing the 2040 Plan.

Without additional information on how Klein arrived at his legal findings, Larkin wrote, "the record is insufficient for this court to determine whether the district court properly exercised its discretion."

Jack Perry, an attorney representing the groups who sued the city, welcomed the Court of Appeals ruling.

"We are very, very pleased that they, like Judge Klein and the Supreme Court before that, are giving teeth to MERA, the state's first and longest environmental protection statute," Perry said. "That's good for the environment. It's good for the citizens of Minneapolis, and it's good for our clients."

Anderson said the city will continue to apply the 2040 Plan standards and requirements to proposed development projects.

"We disagree with the Court of Appeals' conclusion that the plaintiffs satisfied their burden to show that the 2040 Plan is inconsistent with state environmental laws," Anderson said. "The 2040 Plan has been nationally recognized by policy experts as a major step forward for climate action, and we are confident that the 2040 Plan will have enduring, positive environmental impacts."