The RSL says it is unhappy some veterans plan to use Anzac Day as a day of protest.
Organisers claim up to 17,000 veterans are backing a campaign to highlight the plight of serving and ex-servicepeople denied government medical help.
They plan to protest peacefully by wearing orange ribbons, caps or armbands during Anzac Day marches.
But the president of the West Australia's RSL, Bill Gaynor, says the day should be one for commemoration.
"We're not going to stop them wearing it, we're a democratic society. That's what we went away to fight for," he said.
"But, once again, I think there's a need for a bit of responsibility to be accepted by these people in selecting a day which, to veterans, is seen as a day when we honour our fallen soldiers.