Cannes, one of France’s main cruise destinations, said it will impose a sulfur cap on cruise ship calls in 2020.

Mayor David Lisnard told Reuters that the port will ban ships that do not respect a .1 percent cap on sulfur emissions in an effort to improve air quality. 

To comply, cruise operators would need to burn more expensive marine gas oil, or LNG, or use scrubber technology.

Earlier this year, Norwegian Cruise Line Holdings inked an environmental charter agreement with the port, recognizing cruise operators that go above and beyond in environmental protection, according to a statement.