Italy adopted a tough law against illegal immigration on Thursday, including a measure allowing citizens to mount their own patrols, despite fierce criticism from rights groups and the Vatican.
The European Commission announced it would examine the new measures to determine whether they comply with EU norms, warning that "automatic expulsion rules for entire categories are not acceptable".
Italian Prime Minister Silvio Berlusconi had made tougher immigration rules a cornerstone of the election campaign that saw him returned to power in May last year.
The senate, Italy's upper parliamentary chamber, endorsed a vote by the lower house in May bringing the package of measures into full force with 157 in favour, 124 against and three abstentions.
Under the new law, illegal immigration becomes a criminal offence; anyone caught housing an illegal immigrant could face jail; and parents registering a baby's birth have to present papers to show they are legal residents.
During its slow passage through Parliament, the opposition denounced the measures as reminiscent of Italy's fascist era.
Perhaps the most controversial measure permits "citizens groups" to mount patrols on the lookout for public order offences.
After objections that they would be little more than vigilante groups, the local authorities will monitor their activities.
The measure was particularly sought by the fiercely anti-immigration Northern League, part of Berlusconi's right-wing coalition government. The Northern League has a strong presence in the richer northern part of the country.
In Parliament, the opposition put up a bitter fight against the Bill.
Dario Franceschini, leader of the Democratic Party, compared it to the racial purity laws introduced by Benito Mussolini's fascist regime in the 1930s onwards.
Interior Minister Roberto Maroni, a senior figure in the League, dismissed the charge as "laughable".
The new law makes illegal immigration a criminal offence punishable by a fine of between €5,000 and €10,000 and immediate expulsion.
Mr Berlusconi had originally intended to make it an imprisonable offence, but was forced to reconsider because of overcrowding in the prison system, which has reached record levels.
Parents will also have to present their passport or residency permit when they declare the birth of a child, which some critics have warned could lead to a generation of "invisible" children growing up outside the system.
The new law would "deprive children of their most basic rights," said Raffaele Salinari, the president of the Italian branch of Terre des Hommes, a campaign group dedicated to protecting the rights of children.
It also extends the period of detention for illegal immigrations to six months from the current two months to allow more time for them to be identified so they can be sent back to their home country.