Around 22 people were infected, with three hospitalised, after people at the Glasgow entertainment venue ate undercooked burgers from an outlet in January.
Levy Restaurants was held responsible for the outbreak by the Public Health Protection Unit in a report.
Glasgow City Council is to take no further action after being reassured the firm had made changes to the way it prepares food.
But Professor Hugh Pennington, emeritus professor of bacteriology at Aberdeen University, said he is surprised the city council is to take no legal action.
He said: "They have to pay a price by appearing in court."
He wants "rigorous" action to reassure the public.
Levy's owners Compass Group said it took food hygiene very seriously and had robust systems in place to ensure the highest standards are maintained.