The campaign group trying to prevent Manchester City Council closing the right of way between Central Library and the Town Hall Extension will decide next week whether to begin formal judicial review proceedings.
An update to 'friends and supporters of Library Walk' posted on Facebook on Wednesday said the group has been accessing pro bono legal advice since losing the planning inquiry into the stopping up order.
Campaign organiser Morag Rose said 'we believe we have strong grounds to challenge this decision by a judical review.'
A challenge could either be made on 'a technical point about whether the link building is "substantially complete"' as claimed by the Planning Inspector in his decision letter, or a 'wider public interest argument'.
Rose added: "We have issued a pre action protocol, which is part of the legal process, but does not commit us to further action."
The group must decide whether it wishes to proceed with a judicial review by Wednesday 22 April.
Rose added: "If we proceed it will be in the name of an individual and they will face considerable financial risks if we lose and costs are applied (the best guess is around £50,000 but it could be more). If we win we will obviously not face costs and we will have saved Library Walk!"
The council commissioned Simpson Haugh & Partners to design the new structure between the two buildings as part of the renovation of the area. The doors of the new installation across the walkway would be open during the day but closed between 10pm and 6am, to protect public safety, the council said.
Campaigners opposed the public path stopping up order but inspector Mark Yates, who held an inquiry in November 2014, decided the council's planning permission should stand. There were 123 objections to the stopping up order at the inquiry.