Salvini, who is also Italy's deputy prime minister, is being investigated for abuse of office, kidnapping and illegal arrest, after forcing the migrants to stay on the ship at the Sicilian port of Catania for almost a week.
The Coast Guard ship, Ubaldo Diciotti, rescued an estimated 190 migrants on August 15 from an overcrowded boat off the coast of the island of Lampedusa after they were refused entry to Malta.
Thirteen were taken for medical treatment, while 27 minors were allowed to disembark once the ship arrived in Sicily.
However, Salvini refused to allow the remaining migrants to leave the boat until Italy was given assurances that other European nations would take them in.
Salvini's decision to allow the remaining migrants to disembark over the weekend came amid strong criticism, including from several jurists and magistrates, who said Italy was in clear violation of some fundamental norms of national, community and international law.
The prosecutor of Agrigento (in Sicily), Luigi Patronaggio said: "Any limitation of personal freedom must come to terms with the rules and regulations of the European Convention for the Protection of Human Rights, the Constitution, the Penal Code and the Code of Criminal Procedure".
But what laws was Salvini actually violating by keeping the migrants on the ship?
Italy's national ombudsman for the rights of the detained people, Mauro Palma, said the migrants are "de facto deprived of freedom without any legal basis or judicial oversight". He claims Italy is violating:
1.European Convention for the Protection of Human Rights (ECHR)
Article 3 reiterates the "prohibition of inhuman and degrading treatment, especially if vulnerable persons such as children or traumatized persons are involved; in article 5 it is written that every person has the right to freedom and security and no one can be deprived of it without reasons;
2. Article 13 of the Constitution
"No form of detention, inspection or personal search, nor any other restriction of personal liberty, except by reasoned act of judicial authority ". The cases of urgency and necessity must be cancelled after 48 hours;
3. Article 10 of the Constitution
"The Italian legal system conforms to the generally recognized norms of international law. The legal status of the foreigner is regulated by law in accordance with international norms and treaties. The foreigner, who is prevented in his country from the effective exercise of democratic freedoms guaranteed by the Italian Constitution, has the right to asylum in the territory of the Republic, according to the conditions established by law".
4. Geneva Convention, Community Law and Italian Law
Palma said that the treatment reserved for migrants so far stands in contrast to the full effectiveness of the right to access the asylum procedure. Their detention on board cannot therefore be ascribed to the return directive: the lack of authorization for disembarkation, in fact, prevents the assessment of individual situations.
Most of the migrants, moreover, are Eritrean nationals and therefore in "evident need of international protection", according to the terminology used by the European Commission in the procedure of operational relocation until September 2017.
5. Article 33 of the Geneva Convention
Prohibits an asylum seeker or a refugee from being expelled or refused in any way "[...] to the borders of territories where his life or freedom would be threatened [...]" (in this in case Libya is not considered a safe haven).
6. Criminal Code
The investigation, conducted by the prosecutor of the city of Agrigento, was launched against “unknowns”, however it is clear that if the magistrates were to go ahead with a judicial proceeding, Salvini could end up under investigation, being the only one responsible for the landing ban.
7. Code of Navigation, Article 83
"The Minister of Transport and Navigation may restrict or prohibit the transit and parking of merchant ships in the territorial sea, for reasons of public order, safety of navigation and, in consultation with the Minister of environment, for reasons of protection of the marine environment, determining the areas to which the prohibition extends".
Fulvio Vassallo, an expert on asylum law from the University of Palermo, said Italy was facing the possibility of violating article 5 of the European convention on human rights.
In an interview with Radio 24, he said: “This is an illegal detention and asylum seekers detained for more than 48 hours should be immediately released and should be given the opportunity to apply for refugee status.”
However, continues Vassallo, you cannot change rules "tweeted or disclosed on Facebook" as it would require parliamentary action.
Finally, "minor subjects, pregnant women or asylum seekers" are prohibited from being returned to the country from which they fled under law 47/2017 of the code.
8.International Convention on Maritime Search and Rescue (SAR, signed in Hamburg in 1979)
Vassallo points out how the search and rescue operations - as evidenced by the decree rejecting the seizure of the NGO Proactiva Open Arms ship a few months ago - it must complete and end with the landing in a safe place as provided by the convention signed in Hamburg in 1979.
Lawyer and minister for the Public Administration Giulia Bongiorno, member of the executive, on Italian news channel La7 on Thursday said Salvini, “is not racist, but rigorous”
Against the migrants disembarking, she said: "As part of the duties of a minister, [what Salvini is doing] falls within the duties of protecting the community in situations where there could be a disturbance for public order."