The mystery of the sudden crackdown in Tisbury on businesses flying “open” flags has taken on the air of a whodunit, with restaurant proprietors suspecting it was initiated to harm their trade.

Enforcement of a bylaw relating to signs for commercial premises, which was ignored for years if not decades and of which most town officials, including selectmen, were unaware, began suddenly a couple of weeks ago.

The town building and zoning inspector Kenneth Barwick was the man doing the enforcing.

But one thing which became clear on Tuesday night, when the matter came up for discussion before the selectmen, was that Mr. Barwick was not the initiator of the action.

He was acting, he said, on a complaint from someone in another town department, who believed the flags were in violation of the town bylaw. Mr. Barwick did not name the person who made the complaint.

Another thing which appears clear is that the original target of the complaint was one restaurant in particular, the popular Little House Café, which has done a brisk trade on State Road since it opened a year ago.

“I think we’re at the root of this problem,” restaurant co-owner Steven Carreiro, told the board. “I want to know who dug up that crazy bylaw. It seems a little foul to me. Someone’s got an agenda.”

A long discussion then explored the arcane details of the rules for signs in general, and flags in particular.

A formula allows signs proportionate to the size of a business’s frontage; flags are considered advertising and are included in the calculation. The formula varies according to the zoning of the area in which the business operates. But a national flag, of any size and of any nation, is exempt.

This explains why the Scottish Bakehouse — which also was told by Mr. Barwick to take down its “open” flag — now flies the flag of Scotland. And why Rocco’s Pizza, in the Tisbury Marketplace, now flies the flags of Italy and the United States.

It also explains why the owners of the Little House had to get out the scissors and prune their flag to eight square feet, so it became legal.

Little House co-owner Jenik Khelalfa Munafo said after the meeting that they first learned they had a problem with the law when Mr. Barwick came in on the Friday of Memorial Day weekend.

“We were the first ones told the flag had to come down,” she said.

“We pointed out to him there were lots of premises in town that had them up. Ken didn’t even realize it at the time.

“Almost every restaurant had a flag out,” she said. “We didn’t understand why we were being singled out. We’ve had it out since we opened almost a year ago and others have had theirs out for years and years before that,” she said.

The bylaw dates to May 23, 1972, Mr. Barwick said.

The building inspector subsequently visited, by his best count, some 25 Tisbury businesses which had the flags.

He also went to the town planning board to discuss the whole subject of signs and seek clarification of the law. There is, for example, a prohibition on moving signs. Given that a flag moves on a breezy day, did it qualify as a moving sign? The answer was no

Meanwhile, the Little House owners took down their “open” flag after Mr. Barwick left, and initially replaced it with an American flag. Later, after another conversation with Mr. Barwick, they replaced the American flag with the cut-down “open” flag. They obtained the necessary permit.

But they still were unhappy.

“It’s such a stupid bylaw. It’s not business-friendly at all,” said Ms. Munafo.

It was clear on Tuesday evening that the selectmen shared her view.

Selectman Jeff Kristal came close to telling all the parties to ignore the law. “If it ain’t broke, don’t fix it,” he said. And to Mr. Barwick, he said: “Running around taking flags down is not the best use of your time.”

Board chairman Geoghan Coogan concurred, but sympathized with Mr. Barwick, saying there was no point “yelling at you” for enforcing the law.

Selectman Tristan Israel also pronounced himself “certainly sympathetic” with the business owners.

He encouraged them to go to the planning board with their complaints and push for a change to the bylaw. It only takes 10 people to get an article on a town meeting warrant, he pointed out.

That was little comfort to the owners who must wait 10 months for the prospect of change.

As to the original mystery of who filed the complaint that started all this, Mr. Barwick denied knowledge.