Religious law vs. human rights: child brides
Sharia isn't the only kind of religious law that permits child brides. Until 1929 Church of England ministers could marry 12-year-olds in Britain. And until 1983 a quiet loophole in Catholic canon law permitted priests to marry off brides of 12, as well. Now the minimum age allowed by the Vatican for young girls to marry is 14.
Early marriage for girls is permitted in Catholic canon law and the Muslim sharia. As well as dropping out of school, and increasing the risk of abuse, early marriage results in early motherhood, which can lead to death and permanent disability in both child mothers and their children. 
Religious law can give its blessing to this human rights violation. A flagrant example if this is the child brides sanctioned by sharia. Mohammad Ali Isfenani, chairman of Iran's legal affairs committee, said, "We must regard 9 as being the appropriate age for a girl to have reached puberty and qualified to get married. To do otherwise would be to contradict and challenge Islamic Sharia law." After all, according to Islamic scriptures, the Prophet Muhammad marryied a six-year-old bride, with whom he consummated the marriage when she was only nine years old. 
In Malaysia Muslim girls are allowed, with parental permission, to marry at 12, even though the legal minimum for non-Muslim brides in such cases is 16. Nazri Aziz, the Malaysian minister responsible for legal affairs, said the government had no plans to amend the law regarding the minimum legal age of marriage “because it concerns Islamic law.” 
Little wonder, then, that some imams and sharia courts in Britain have performed religious marriages on child brides, even though this is illegal there. 
In the past child brides were also sanctioned by other kinds of religious law. Until 1929 when the British Marriage Act raised the age, Church of England ministers, who long had the monopoly on performing the ceremony, happily married girls as young as 12.  And until 1983 Roman Catholic canon law also permitted 12-year-old brides, so long as the father gave his permission. Otherwise they had to be at least 14, as is the case today.  This religious justification allowed places like the Canadian Province of Quebec to permit the marriage of little girls of 12.  And in 2001 Monsignor Maurice Dooley from Ireland said priests could ignore state law to marry 14-year-old girls, according to church laws. 
1. "The perils of early motherhood", hildren having children, Save the Children's Fund, 2004, pp. 10-15. http://www.savethechildren.org/atf/cf/%7B9def2ebe-10ae-432c-9bd0-df91d2eba74a%7D/SOWM_2004_final.pdf
2. "Child Bride Practice Rising In Iran, Parliament Seeks To Lower Girl's Legal Marriage Age To 9", International Business Times, 2012-08-30 http://www.ibtimes.com/child-bride-practice-rising-iran-parliament-seeks-lower-girls-legal-marriage-age-9-760263
3. "Calls to End Child Marriages in Malaysia After 12-Year-Old Weds", New York Times, 2012-11-26 http://www.nytimes.com/2012/11/27/world/asia/calls-to-end-child-marriages-in-malaysia-after-12-year-old-weds.html
4. "Islington girls forced into marriage at the age of nine", Islington Tribune, 2012-01-27. http://www.islingtontribune.com/news/2012/jan/islington-girls-forced-marriage-age-nine
"Forced marriage: Girl aged five among 400 minors helped", BBC Asian Network, 2012-03-29. http://www.bbc.co.uk/news/uk-17534262
[The Sunday Times investigative report is behind a paywall, but below are an excerpt and a summary.]
"Sunday Times front page story on ‘Islamic child brides’ ", Engage, 2012-09-12.
"The British child brides: Muslim mosque leaders agree to marry girl of 12... so long as parents don't tell anyone", Daily Mail, 2012-09-09. http://www.dailymail.co.uk/news/article-2200555/The-British-child-brides-Muslim-mosque-leaders-agree-marry-girl-12--long-parents-dont-tell-anyone.html
5. The UK government site won't admit that until 1929 Britain's law and its state church permitted 12-year-old brides: "The law of marriage" http://www.parliament.uk/about/living-heritage/transformingsociety/private-lives/relationships/overview/lawofmarriage-/
6. The Roman Catholic canon (church) law, in force until 1983, avoided saying outright that 12-year-old girls could be married off. Although in the fourth section it sets the minimum for girls at 14 (1067, p. 1) It defines puberty for girls as occuring at age 12 (1.88.2) and says that they can exercise those rights which the (civil) law has not removed from "the father's power" (prerogatives). (1.89) Where Church influence was strong enough that child marriages were tolerated, this amounted to permission to let a girl marry as soon as she had attained the age that the Church defined as "puberty". (It's best to ignore the English "translation" of this French edition, as it's a bizarre attempt by some machine.)
The 1983 version of canon law, now in force, gives 14 for the minimum age of a girl and 16 for a boy. (Can. 1083 §1) (It calls them a "woman" and a "man".)
7. This loophole in Canon Law was used to permit 12-year-old child brides in Quebec before the "Quiet Revolution" of the 1960s began the secularisation of the province..
"Civil Marriage", Catholic Encyclopedia, 1914 http://www.newadvent.org/cathen/09691b.htm "The minimum age for marriage in the Province of Quebec is fourteen for males and twelve for females."
8. Ciaran Byrne, “Controversial cleric a 'grade A1 idiot', says colleague”, Irish Independent, 20 March 2010. http://www.independent.ie/national-news/controversial-cleric-a-grade-a1-idiot-says-colleague-2105732.html