The Peoples Party deserves praise for trying to protect women in the country. It has passed the minimum marriage age bill for girls, requiring them to be married only after the age of eighteen. The only problem is that it's virtually impossible to ensure that this law is observed. One reason for this is that people in the rural areas of the country do not register the births of their children. But the main reason is that people believe that Islam requires that girls should be married as soon as they reach puberty (which most do at the age of twelve).
I once heard a judge say that he has no choice but to allow marriage of underage girls as that is the law of Sharia, even if the country's law prohibits the marriage of girls who are not yet eighteen. Naturally, if an educated man has this opinion, what can a layman say?
There is another reason: the sale of female children by men who don't earn enough to survive or buy narcotics. A maid servant once decided to go to the court for getting a divorce from her husband. the man came with ten others, demanding that his three female children should be handed over to him. He didn't want his wife back. It turned out that he'd already sold the girls and wanted to get the money from the buyers so he could continue buying drugs. In such a scenario, it's impossible to protect Pakistani girls.