Since 2004, she has served as the United Nations' Special Rapporteur on human trafficking. She is also known for her views on prostitution. In her report for the United Nations Commission on Human Rights, she says:
- “The act of prostitution by definition joins together two forms of social power (sex and money) in one interaction. In both realms (sexuality and economics) men hold substantial and systematic power over women. In prostitution, these power disparities merge in an act which both assigns and reaffirms the dominant social status of men over the subordinated social status of women.”
- “The demand for commercial sex is often further grounded in social power disparities of race, nationality, caste and colour.” 
In 2007, Huda was brought before a Bangladeshi court on bribery charges filed by the Anti-Corruption Commission, whereupon she was sentenced to three years imprisonment as an accomplice to a bribe in the amount of Taka 2.40 crore (approximately US$400,000) for which her husband was convicted of abuse of power and corruption. As a result of the conviction, Huda was prevented from leaving Bangladesh despite apparently enjoying diplomatic privileges as a UN rights expert which prevent her arrest or detention.
The UN Special Rapporteur on the independence of the judges and lawyers issued a statement on September 2, 2007 expressing concern that Huda was not given a fair trial. He said it received reports indicating that the right to legal representation and the independence of the court were severely affected during her trial. 'Defense lawyers felt pressured, they had no opportunity to visit her in prison and could only meet with her at the end of the hearings. They also had difficulties accessing the case files and other relevant information, thus compromising their ability to ensure an adequate defence.'
- Huda, S "Report of the Special Rapporteur on the human rights aspects of the victims of trafficking in persons, especially women and children, Sigma Huda" for the United Nations Commission on Human Rights, February 2006
- "Huda gets 7 years, Sigma 3 yrs for graft". Daily Star. 2007-08-28. Retrieved 2010-10-09.
- http://www.asiantribune.com/index.php?q=node/7220/ Asia Tribune: United Nations Human Rights Special Rapporteur expresses concern about Sigma Huda’s trial in Bangladesh