Thousands of bikers heading to South Dakota’s 10-day Sturgis Motorcycle Rally will not be allowed through Cheyenne River Sioux checkpoints, a spokesman for the Native American group said on Saturday. The decision to prevent access across tribal lands to the annual rally, which could attract as many as 250,000 bikers amid fears it could lead to a massive, regional coronavirus outbreak, comes as part of larger Covid-19 prevention policy. The policy has pitted seven tribes that make up the Great Sioux Nation against federal and state authorities, which both claim the checkpoints are illegal. A duty officer for the Cheyenne River Sioux told the Guardian on Saturday that only commercial and emergency vehicles will be let through the checkpoints onto reservation land. A number of bikers had tried to enter but had been turned back, they said. Other reservations in the region, including the Oglala Sioux, were also turning away bikers that had attempted routes to Sturgis that pass through sovereign land. Under Cheyenne River tribal guidelines non-residents driving non-commercial out-of-state vehicles are never allowed through the reservation. During the rally, non-commercial vehicles with South Dakota plates are also not allowed through. The clampdown comes as fears mount that mask-free bikers visiting Sturgis for the largest gathering of people since the start of the Covid-19 epidemic could spread the virus to tribal groups that are already experiencing a rise in cases. Oglala Sioux recorded 163 cases last week, while the Cheyenne River Sioux has seen cases rise to 79, according to the tribe’s website. The restrictions come as local law enforcement reported a convergence of bikers from all directions. According to reports, many bikers heading for Sturgis expressed defiance at rules and restrictions that have marked life during the coronavirus pandemic. While South Dakota has fared better than most states – it ranks 38th in Covid deaths per capita, according to a Reuters tally – cases have risen in recent weeks as hotspots move into the midwest. During the rally, people are expected to cram bars and pack concerts with at least 34 acts playing. “Screw COVID,” read the design on one T-shirt on sale. “I went to Sturgis.” Stephen Sample, who rode his Harley-Davidson from Arizona, told the Associated Press that the event was a break from the routine of the last several months. “I don’t want to die, but I don’t want to be cooped up all my life either,” Sample, 66, said, adding that he had weighed the risks of navigating the crowds, but the same thrill-seeking that attracted him to riding motorcycles seemed to win out. “I think we’re all willing to take a chance,” he said, but acknowledged the trip “could be a major mistake.” South Dakota’s Republican governor, Kristi Noem, has supported holding the Sturgis rally, pointing out that no virus outbreak was documented from the several thousand people who turned out to see Donald Trump at Mount Rushmore last month. The rally is marking its 80th anniversary and typically injects $800m into South Dakota’s economy. Meade county sheriff, Rob Merwin, said: “It’s going to be a lot of people and a lot of motorcycles all over the place. People are tired of being penned up by this pandemic.” On Friday, a worker at the event told the Guardian crowds seemed larger than in previous years and warned that Sturgis attendees were paying little heed to medical advice. “I’ve not seen one single person wearing a mask,” said bartender Jessica Christian, 29. “It’s just pretty much the mentality that, ‘If I get it, I get it.’” “In downtown Sturgis it’s just madness,” Christian added. “People not socially distancing, everybody touching each other. It’ll be interesting to see how that turns out.” Over 60% of Sturgis 6,900 residents who responded to a city council survey in May said they wanted the rally canceled. A month later, the council voted to move ahead, although it canceled all city-sponsored events associated with the rally and included measures such as hand-sanitizing stations. Sturgis mayor Mark Carstensen said throughout the pandemic, “the state of South Dakota has been the freedom state and the city of Sturgis has stayed true to that”.