Hi,
As far as I know it depends of your permit, if your permit is A, B , C or Ci you can work, otherwise I suggest you to go to the bureau cantonal de la population and ask them. 
Cheers!

Internships do not fall under the 20hours work thing. The 20 hours work rule is for when you are actually in school. Internships are considered work experienc so you can do normal 40 hours a week

If you are not paid, I understand the authorities do not even need to be notified or get involved. The 20 hours per week rule applies for paid work, internship or not.

Thank you all for replying and helping me out. My situation is that I am currently enrolled as a student, and at the same time i want to do the intership in 80% of the time. I just want to be legally compliant with swiss law but i can not find a disposition in the loi pour les etrangers which refers to my situation.

Without knowing your nationality and where, what and how long you have been a student in Geneva, etc., it is not easy to give you any concrete advice, so why don’t you go to the Office de la Population and get clarification from the  people who are paid to provide such information?

All the best, R.

Hi Hermi,

They recently changed the law in January 2016 so that foreign students attending any Geneva university are permitted to only work for a total of 15 hours per week for any work that relates to your study. If it's for work that does not relate to your studies such as waitressing/bartending, I think you can only do that type of work during the summer and the hours are still limited. This means that even if you commence working at an international organization which falls outside of Swiss labor laws, you can still only work only 15 hrs/week; it applies foreign students studying at Geneva universities only. The law is designed so that foreigners who are here with a student permit are truly only focsing on getting their degree. Your university should know the exact law and you would need their permission to engage in any sort of work, granted it is legal.