The Jacobite, which runs from Fort William to Mallaig, has been suspended in the past because of concerns over its hinged carriage doors.
A train service that featured in several Harry Potter movies can resume after being granted a temporary exemption to a safety rule.
The Office of Rail and Road (ORR) said the Jacobite – often referred to as the Hogwarts Express – can run until the end of November.
The popular tourist attraction, operated by West Coast Railways, has often been suspended in recent weeks after safety inspectors found an issue with the hinged doors of its carriages.
It runs between Mallaig and Fort William across the Glenfinnan Viaduct in the Scottish Highlands.
The ORR said in a statement: “Following an inspection of West Coast Railway Company Limited’s (WCRCL) proposed safety arrangements for the Jacobite service on August 8, ORR has granted it a new exemption certificate which will allow the Jacobite to recommence operation.
“This exemption certificate is required for all train operators who want to use hinged door carriages without central door locking fitted.
“WCRCL’s exemption certificate is granted for a timebound period from August 8 to November 30 to enable it to honour its bookings and reflects the interests of its employees whilst its claim for judicial review is determined.”