The Writers Guild of America has acknowledged that John Ridley’s (above) script for “12 Years a Slave” was ruled ineligible for WGA awards consideration because Ridley resigned from the guild during the bitter 2007-08 strike.

The exclusion is a reminder of the many rifts that remain from the 100-day work stoppage.

Ridley’s screenplay has received plenty of recognition during awards season with nominations for BAFTA, the Golden Globes, Independent Spirit and the USC Scripter awards. Ridley, who based the script on the autobiography by Solomon Northup, is widely viewed as a probable Oscar nominee in the adapted screenplay category.

But the WGA did not include “12 Years a Slave” on last month’s ballot of 44 eligible adapted screenplays and its announcement of the nominees included language spelling out that nominated scripts had to have been produced under the guild’s collective bargaining agreement or under that of a sister guild in Canada, Ireland, New Zealand or the U.K.

The production companies on “12 Years a Slave” include Brad Pitt’s Plan B and Regency Enterprises — both which are guild signatories, which would make the script eligible for awards consideration. But WGA West spokesman Neal Sacharow told Variety that Ridley’s move to file for financial core status during the strike had disqualified the script.

“It is WGAW Board policy that writers who renounce their union membership are ineligible for Writers Guild Awards,” he said. “Mr. Ridley resigned from the Guild during the 2007-08 strike.”

Ridley has not commented about the exclusion of “12 Years a Slave.” He had gone public six years ago with his decision during the latter stages of the 100-day strike, asserting that he disagreed with the tactics of the guild’s leadership and their unwillingness to tolerate dissent.

In an op-ed published in the Los Angeles Times, Ridley wrote, “I lived with the vitriol stirred by my questioning. Never mind that I’ve walked the picket lines. Never mind I’ve donated to the strike fund. The first rule of Strike Club: Never talk about Strike Club! That would be fine for an organization whose membership joins voluntarily. But when membership is compulsory, free expression must be accommodated. The obligation of the union is to protect, not crush, the minority view.”

By going financial core, writers withhold the portion of dues spent by the WGA on noncontract activities — while still being able to write scripts. Fi-core writers pay dues that are 1.9% less than regular members; they also can’t run for guild office or vote on contracts or in any WGA election.

The strike generated hard feelings among writers. Two months after the strike ended, the WGA leadership publicly identified 28 writers — most of them working on soap operas — who resigned from the guild during the work stoppage by filing for financial core status.

At the time, Ridley — whose credits include “Three Kings” and “Undercover Brother”  — was the highest-profile writer among the 28 named.

The unusual disclosure of the 28 names came in an angry letter to members from then-WGA West president Patric Verrone and WGA East prexy Michael Winship, who opened the letter by citing the high level of compliance with strike rules among the 10,500 WGA members.

“Yet among the many there were a puny few who chose to do otherwise, who consciously and selfishly decided to place their own narrow interests over the greater good,” Verrone and Winship wrote. “This handful of members who went financial core, resigning from the union yet continuing to receive the benefits of a union contract, must be held at arm’s length by the rest of us and judged accountable for what they are — strikebreakers whose actions placed everything for which we fought so hard at risk.”

The presidents also revealed in the letter that those going fi-core would be ineligible for WGA awards.

“Those who went financial core did not share in the adversity; and should not share in our victory,” they said. “They cannot vote in our elections, run for Guild office, attend Guild meetings and other events, or participate in the Writers Guild Awards.”

The fi-core issue received increased recognition before the strike when the Alliance of Motion Picture & Television Producers explained on its web site how to file for fi-core status in order to continue writing during the strike. The AMPTP pointed out at the time that WGA members who went fi-core could not be disciplined for working during a strike.

When the 28 names were disclosed, some writers characterized the decision to go public with the names as a blacklisting tactic while others endorsed the move as a necessary component of union discipline.

George Clooney had also gone fi-core in 2007 prior to the strike as a result of the WGA’s decision in a credit arbitration vote that Clooney would not get screen credit on “Leatherheads.” Clooney didn’t appeal the WGA ruling and kept his action quiet because he didn’t want the filing seen as his having split ranks with the union over the labor dispute.