As the Italian government considers how to handle massive cruise ships overrunning Venice, the United Nations Educational, Scientific and Cultural Organization (UNESCO) has finally stepped into the fray, making clear their opinion that oversize vessels should be banned from the lagoon in order to protect the port city and World Heritage Site, reports the Art Newspaper.

This is just the latest bout in the battle between preservationists and the city’s booming tourism sector. An initial round of restrictions on cruise ships larger than 40,000 tons was overturned in March. In August, the government announced plans to reroute cruise ships so they no longer pass through the heart of the city.

However, the proposal would necessitate dredging the shallow Canale Contorta Sant’Angelo, increasing the channel’s width seven-fold and making it four times as deep. Previous dredging done in the 1960s has since been shown to have increased flooding and had other adverse environmental effects, leading many to oppose the new plan.

Environmental scientists have been vocal in their opposition to any additional dredging, which would make the quiet lagoon much more like the open sea, endangering the already  fragile city. Their concerns are shared by at least 27,000 petitioners and 40 senators. Even before the plan was announced, a star-studded petition signed by the likes of Tilda Swinton, Norman Foster, and Carolina Herrera advocating for the ships’ ban had also been circulating.

Now, UNESCO’s World Heritage Committee has passed resolutions that will place Venice on the World Heritage in Danger list if the Italian government does not actively protect what the committee describes as “an extraordinary architectural masterpiece.” UNESCO is opposed to any plan that would dramatically alter the land- and seascape surrounding the lagoon, and urges developers to carry out careful environmental impact assessments before beginning any large-scale projects.

The Italian government is accepting environmental commentary on the project through Friday, October 17.