The Orange Order is facing increased pressure to drop its ban on face-to-face talks with nationalist residents' groups and the Parades Commission.
The South African mediator, Mr Brian Currin, a human rights expert brought in to help resolve the Drumcree dispute, has warned of "dire" consequences if the order continues to reject direct dialogue.
In a written submission to the order, Mr Currin pointed out that following European human rights legislation being enshrined in British law, further bans on parades may follow.
He argues that the only alternative is for Orangemen to join a "collaborative" effort which would include residents and the Parades Commission.
Mr Currin said: "The Parades Commission provides a key to the preservation of cultural diversity in Northern Ireland.
"If that key is thrown away, the consequences for Orangeism, its culture and traditions will be dire."
The Grand Lodge of Ireland met in east Belfast at the weekend to discuss the order's policy on negotiations. Mr Currin said the deliberations on engagement with the Parades Commission and residents' groups could be judged as some of "the most important decisions ever taken by the Orange Order".
Grand Lodge general secretary, Mr George Patton, said that while this assessment may be accurate, it was a "terrible indictment of society".
Examining the European Commission's approach in deciding if Article 11 of the Human Rights Convention guarding the freedom of peaceful assembly and association has been breached, Mr Currin noted the ease with which non-violent parades were banned.
"My own conclusion is that in Europe the right to peaceful assembly is a fairly soft right. The interests of public safety, the prevention of disorder and the protection of the rights of others take relatively easy preference."