Dozens of Tunisian activists protested in the port city of Sousse on Sunday to demand the return of nearly 300 containers of household waste illegally imported from Italy.
Tunisian customs officials last summer seized 282 containers that had been shipped from Italy in the guise of plastic scrap for industrial recycling.
But the containers were found to contain household waste, which is barred from import under Tunisian law.
Rome had given the Italian firm that sold the refuse up until last week to retrieve the cargo, but the deadline passed without it doing so, court official Jabbeur Ghnimi said on Thursday.
On Sunday, campaigners gathered at the eastern city's port to demand the trash be repatriated.
"There's no social justice without environmental justice," some chanted.
The affair "is a crime against the Tunisian people," said Majdi Ben Ghazala, a member of Sousse city council.
"We demand that the (Tunisian) authorities show more determination" to have the waste removed.
An activist at the protest, Hamdi Bin Saleh, said a further demonstration was planned for Thursday in front of the Italian embassy in Tunis to demand the rubbish be returned.
The scandal prompted the sacking and arrest of Tunisian environment minister Mustapha Aroui, who along with 25 other people, several of them also in detention, are facing prosecution.
They also include the manager of the Tunisian import firm, who is at large, court official Ghnimi said.
Tunisia has accused the Italian company, Sviluppo Risorse Ambientali Srl, of failing to meet the deadline to remove the containers.
The case shines a spotlight on the global trade in waste as richer countries dump their garbage on poorer ones which, like Tunisia, are often ill-equipped to deal with it.
Interpol warned in August last year that criminal organisations have profited from an "overwhelming" surge in illegal waste shipments, particularly to Asia but also other parts of the world.