She was speaking after a meeting with Derg Valley Victims' Voice on Thursday.
Ms Villiers explained that she does not have the powers to cancel the event in Co Tyrone this weekend, but asked those behind it to think again.
"This parade is damaging to community relations and even at this late stage I would call upon the organisers to think again and call it off," the NI Secretary explained.
"On the issue of legal powers to ban the parade, these are restricted and narrowly defined. The criteria set out in legislation that would enable me to intervene are not satisfied in this case. I realise that will disappoint many but I am bound by the law."
The contentious Tyrone Volunteers Commemoration will be held in Castlederg on Sunday.
There is no doubt that this deeply insensitive parade is causing great hurt and distress to many victims of terrorism in the west Tyrone area and the rest of Northern Ireland.
NI Secretary Theresa Villiers
The annual event will this year coincide with the 40th anniversary of the deaths of IRA men Seamus Harvey and Gerard McGlynn, who died when the car bomb they were transporting to Castlederg detonated early. It exploded across the Irish border in Co Donegal.
Sinn Féin West Tyrone MLA Barry McElduff said: "Theresa Villiers is in no way an independent arbiter in this issue and should stay out of parading issues.
"Instead, in her comments, Ms Villiers has outlined her partisan objections and further endorsed the view that there are a hierarchy of victims when it comes to the conflict in Ireland.
"Sinn Féin believe that there can be no hierarchy of victims and that we all should have the opportunity to remember our dead."
Last week the Parades Commission ruled that the march, which is backed by Sinn Féin but opposed by unionist parties and the SDLP, could go ahead with restrictions.
Organisers of the parade have been told that it will not be allowed to proceed around The Diamond area of the town and that no paramilitary trappings will be permitted.
While the DUP feel that the event should have been banned completely, Sinn Féin has also spoken out against the determination because of the restrictions put in place.
They insist the event does not glorify terrorism and point out that a number of loyal order parades have been allowed to pass through Castlederg, including an Apprentice Boys march which is due to take place the day before the republican event.
A counter-protest has been announced by Sinn Féin for Saturday.
Local councillor Ruairi McHugh said: "The 10th of August will see the 19th loyal order parade in Castlederg this year. Our protest is to highlight the double standards at play and to give a dignified outlet to the anger vented in this community. Once again the on-going disparity of treatment has been allowed to continue in Castlederg."
The Secretary of State can only revoke, amend or confirm a determination by the parades watchdog if the Chief Constable makes a formal request for her to review it.