John Drummond, chief executive of the SGF, said the Scottish government had been "paralysed by procedure".
"Parliamentary niceties have prevented them from spending the money needed to protect shopworkers," he said. "It is shopworkers not the police or politicians who will be expected to enforce the law."
The SGF is helping its members prepare by producing posters and staff briefing notes. It is also encouraging the use of Challenge 21.
Meanwhile, MSPs have expressed concern that no extra resources or trading standards officers are to be made available to impose the law when it comes into force on October 1.