ARLINGTON — Outflanked and surprised, Snohomish County is threatening to sue the city of Arlington if it doesn’t repeal its annexation of Island Crossing that takes effect today.

A Snohomish County lawyer sent a terse two-page letter to the city Monday calling the annexing of the 110-acre property an “illegal” act in violation of state growth management laws.

Snohomish County Council members ordered the letter following an executive session Monday afternoon.

“We don’t believe Arlington has the right to annex it,” Councilman Mike Cooper said. “It appears Arlington is trying to skirt the process by moving forward.”

The letter arrived by fax at City Hall just before 5 p.m. Monday, startling Arlington officials who’ve spent the past five years teamed up with county leaders in a legal fight on the future of Island Crossing.

“We were pretty surprised and shocked by the county’s letter,” spokeswoman Kristin Banfield said.

Confused, too, because last month the city and county celebrated a state Supreme Court decision in their favor that appeared to clear the way for development of the land by its various owners, including auto dealer Dwayne Lane. Reached late Tuesday, Lane said he not seen the letter and could not comment on any of the issues raised by the county.

“For the county to go all the way to the state Supreme Court with us and then a month later, they’ve gone completely the other direction, is confusing and distressing to us,” Banfield said.

The Arlington City Council voted unanimously Nov. 17 to add 210 acres into the city limits, half of which is the controversial swath known as Island Crossing.

Now part of the city are Island Crossing restaurants and gas stations on Highway 530 to the north and mostly fallow farmland along Smokey Point Boulevard. On the south end are homes and businesses along the bluff north of 188th Street NE.

Council members and county planners didn’t learn of the decision until days after it occurred, Cooper said.

“The letter was designed to say, ‘Let’s slow down and let the courts decide,’ ” he said.

Banfield said she wondered how the county could have been caught flatfooted by the city’s action.

“We’ve been talking about this annexation for 17 years,” she said.

The state’s Growth Management Act requires land be within a city’s Urban Growth Area before it can be added. The county contends Island Crossing is not in Arlington’s sphere of influence.

In 2003, Snohomish County did rezone the property from agricultural to commercial uses and place it within the Urban Growth Area of Arlington. But that decision and subsequent actions were frozen when they became the subject of the lawsuit heard by the state Supreme Court.

Opponents of the rezoning wanted the county action tossed out. The city and county argued it was all done legally.

Differing interpretations of the high court decision have turned partners into adversaries.

The city contends the court ruling wiped out opposition and restored the 2003 and 2004 votes by the county.

“We think the Supreme Court was pretty clear. It was telling us pretty clearly that it is all done,” Banfield said.

John Moffat, assistant chief of the civil division in the county prosecuting attorney’s office, disagreed.

The justices upheld the process followed by the county and ordered the Central Puget Sound Growth Management Hearing Board — which threw out the rezoning — to reconsider. That has not occurred, so the county decisions are still on hold.

The city’s conclusion that the court “somehow automatically” put Island Crossing in the city’s Urban Growth Area is “a legally unsupportable conclusion,” he wrote.

Thus annexation cannot proceed unless and until the county acts as it did in 2003.

That may be asking a lot from the current political makeup of the County Council.

Then Republicans had the majority; today Democrats are in charge. Chairman Dave Somers and Cooper are outspoken opponents of allowing the land to be rezoned and allowed into the city for development.

“We never rezoned it and a majority of the current County Council would not likely do it today,” Cooper said.

Reporter Jerry Cornfield: 360-352-8623 or jcornfield@heraldnet.com.