If legalization doesn't curb trafficking immediately, it would do it in certain period of time. If rights are provided, they can be demanded for but if someone has no rights, then they will keep getting abused. After prostitution is legalized, at least some trafficked prostitutes and supporting NGOs can raise their voice in the court of law. Hence, it is in best interest of human right promoters to legalize prostitution.
It would allow the people that traffic others out as prostitution a chance to hire women actually willing to do the work, instead of trying to find someone who may or may not be underage. Since it would become a legitimate business it would require laws and regulations as well which mean minors would not be able to participate.
Legalizing prostitution will help to reduce and hopefully someday eliminate sex trafficking in a number of ways. First, with a legal alternative most people will not choose to go to an illegal and unethical trafficker. By reducing demand and financial resources, trafficking will no longer offer the allure of financial gains and it will not be worth it to the traffickers to risk the jail time with little reward. Also, the reduced demand on police will allow them additional time to focus on the traffickers, and more investigation time will ultimately lead to additional arrests and reduced trafficking.
People who are willing to buy and sell other human beings are not necessarily looking for sex whenever they want. It's about being able to own and control another human being and treating them like an animal. Even if you disagree with me, then think about it this way: Why would someone legally pay for sex when they can get it for free with however they want at anytime they want?
It will only make things worse and legal. Women will still be exploited, and if they leave the business of legal prostitution, they'll still be desperate to find a job and some money. Prostitution is a sad reflection on society and should be prevented at all costs. It is an exploit on people in poverty.
No, it will not help. If anything, legalizing prostitution will merely open a legitimate destination for many of the men and women trafficked every year. People are kidnapped or forced into the sex industry all over the globe, and legalizing it in one country will not solve this problem. Furthermore, legalizing prostitution may of the opposite effect, as it will provide a legal avenue by which to traffic more people.