They are the guerrilla golfers of Stornoway: a small and unassuming group of rebels who over the last few months have done what golfers anywhere else in Britain do naturally – played the game on Sunday.

But each time this group carry their golf bags on to this compact but windswept 18-hole course on the sabbath, it is a deliberate act of defiance. On the Presbyterian islands of Lewis and Harris, Sunday is the one day of the week when playing Scotland's national game is banned.

For the deeply orthodox Protestants of the Western Isles, Stornoway golf course is emerging as one of the last battlegrounds in their increasingly vain fight to keep the sabbath sacrosanct.

And today, a softly spoken community dentist, George MacLeod, walked on to the steep-sided course with a small group of friends for another rebellious round. Elsewhere were others, quietly putting on greens hidden from view.

"I wouldn't say I felt like a revolutionary," MacLeod said. "I would say I just felt like an adult. Why they're telling me I can't play on a Sunday is beyond me."

The rebellion is intensifying. Last Wednesday the club's latest attempt to get a Sunday drinks licence was thrown out. Councillors upheld allegations by church groups that granting the licence would "damage morality", "weaken the integrity of the community" and lead to increases in domestic violence, alcoholism and disorder.

Ordained of God

The Lord's Day Observance Society, the umbrella group for hardline sabbatarians, reminded the board "that they constitute part of the powers that be that are ordained of God … not to weaken the integrity and decency of community. We believe that granting the application would both undermine morality and inhibit the due observance of the Lord's Day."

Ken Galloway, the club's mild-mannered secretary, was exasperated by the vote, which went 6-4 against granting the licence. "Terrible," he said. "Why are so many people intent on blackening the good name of Stornoway golf club?" he asked the committee. "What has this club done to deserve this onslaught?"

Very little, according to Inspector Steven Black of Northern Constabulary. There had only been six minor incidents at the club in 12 years, so the force had no objections to a Sunday licence. "It is a well-run establishment. We do routinely check it and we have no issue with the management of the premises," he told the committee.

Norrie MacDonald, the club captain, says there is little the club can do to stop the unauthorised rounds. As Sunday games are banned by the Stornoway Trust, the club's landlord and owner of 28,000 surrounding hectares, they cannot employ any staff. So the course is unmanned.

It is, MacDonald notes drily, the only course in Scotland where you get a free game on a Sunday. "If someone isn't a member, we can't do anything about it. We can't even charge them a fee," he said.

Ferries and flights

Over the past few years, the sabbatarians have lost a series of crucial battles with privately-owned businesses: ferries and flights now land on Sundays, while pubs and a petrol station in Stornoway are routinely open. All are heavily used.

But critics claim the sabbatarians' influence over publicly-owned leisure centres, swimming pools, golf courses and football pitches remains total: they are the only sports facilities in Britain that remain closed on Sunday for religious reasons.

Western Isles council (Comhairle nan Eilean Sar in Gaelic), which owns all the main sports facilities, remains implacably opposed to Sunday opening.

And across Lewis and Harris, numerous locally-run football pitches, sports centres and golf courses funded by public grants are kept shut by their owners.

Their authority is now being challenged on two fronts. The golf club's members have voted overwhelmingly to press Stornoway Trust for permission to amend their lease to allow Sunday golf. And George MacLeod's wife, Helen, is leading a campaign to get the town's leisure centre open on Sundays, gathering signatures from 300 families on a petition.

The MacLeods, Galloway and MacDonald believe the council is guilty of religious discrimination by allowing one religious position to determine policy, while the funding agencies, particularly Sportscotland, which handles millions of pounds in government and lottery grants, are guilty of hypocrisy.

In the mainly Catholic southern parts of the Western Isles – the Uists, Barra and Benbecula – all the sports facilities are open on Sundays.

Discrimination

The council also operates buses on a Sunday to take people to church, but refuses to run public bus services. And Sportscotland – knowing there are questions about the legality of closing public facilities on a Sunday for religious reasons – continues to give grants to sabbatarian groups.

The agency has been accused of hypocrisy after first refusing to give around £64,000 to Harris golf club because it would be closed on a Sunday, but then backing down after pressure from island politicians – a charge the agency refused to comment on last week. The Stornoway Trust also refused to respond to requests for an interview.

An attempt by Helen MacLeod to legally challenge the leisure centre's Sunday closure failed earlier this year when she was denied legal aid – so the allegation of illegal discrimination remains untested. But she and the golf club say they plan to fight on.

One club member said Sunday golf "could be the last bastion of Sunday observance in the Western Isles."

MacDonald noted: "They can't control the flights, they can't control the ferries and they can't control Scottish licensing laws but they can say you can't play golf on Sunday. And they don't have to give a reason."

All at sea

The simple question of operating ferries between the Isle of Lewis and Ullapool on mainland Scotland on a Sunday caused the last major battle over the preservation of the sabbath.

For generations, conservative Presbyterian churches on the island, particularly the staunchly Calvinist Free Church, bitterly resisted their introduction – a position backed by Western Isles council. The Lord's Day Observance Society collected 3,760 signatures of protest.

But Scotland's largest ferry operator, Caledonian MacBrayne (CalMac), was under heavy pressure to introduce a Sunday service from businesspeople, tourism agencies and non-sabbatarians.

Sunday flights to Stornoway on the island had run for some years and in 2008 a Sunday ferry service began between neighbouring Harris and the islands of Barra and Uist.

CalMac announced in May last year that seven-day sailings would start. The company said it was legally obliged to do so, since the ban breached rules outlawing religious discrimination in the Equality Act 2006. It was, CalMac said, illegal to refuse a service because of the religious views of just one part of the community. Even so, the sailings remain discreet: the mainland ferry arrives at 9pm – well after dark in winter.

• This article has been corrected. Ken Galloway had been incorrectly named as Ken Buchanan.