Workers at a Somerville Starbucks picket Wednesday. (Photo: Starbucks Workers United via Twitter)

Workers walked out of a Somerville Starbucks on Wednesday after getting threats from management for wearing union apparel, according to the Starbucks Workers United labor organization. Staff filed Feb. 24 with the National Labor Relations Board to unionize.

The international coffee shop chain has a reputation for union busting among labor organizers. Locally, they point to a Starbucks in Boston closed permanently Feb. 5, eight months after workers voted to unionize. The chain’s story is that that the location “no longer meets the needs of the business,” according to Boston.com.

The Starbucks that closed Nov. 13 in Cambridge’s Central Square had no known unionization effort underway. A company statement pointed to worker safety as a reason for the closing.

At the Somerville Starbucks at 711-723 Somerville Ave., Wilson Square, workers didn’t just walk out – they picketed.

“Yesterday, [one of us] got written up for wearing her Starbucks Workers United shirt, and today, we got told again we’re not allowed to wear it, even though it is legally protected. So we walked out,” one Somerville worker said Wednesday, according to Starbucks Workers United.

Starbucks management’s attempts to discipline workers for wearing union apparel is a violation of the National Labor Relations Act, which Starbucks has been found in violation of for similar offenses across the country over the course of the national union campaign, the group said.

The company says that graphic T-shirts of any kind are prohibited on staff, and that any union message was beside the point. Workers are given chances to change out of clothing that falls outside company rules – and in this case they did not.

“We respect our partners’ rights to organize and engage in lawful union activities and we fully honor the process laid out by the NLRB to ensure that partners can trust the process is fair and their voice is heard,” a Starbucks spokesperson said Wednesday. “A partner’s involvement in union activity does not exempt them from adhering to the policies and procedures that apply to all partners.”

In other coffee shop news: Former Darwin’s Ltd. workers have changed their plans for opening a worker-owned cafe called the Circus Co-op, the Harvard Crimson’s Caroline K. Hsu reports. They’d been looking at 1629 Cambridge St., Mid-Cambridge, a closed location in the chain, but with the sale of that building are now looking elsewhere, including at the two other former Darwin’s sites.