Yes, you may. However, it is also governed by the laws of each country.
While we encourage an open marketplace, please refrain from selling or auctioning anything that is prohibited from being shipped into Singapore by the Singapore Customs.
If you are unsure, please contact Singapore Customs here.
For Customs for all other countries, please refer to their respective websites for the list and contact information. A search using Google will usually bring you the fastest, and the most fruitful results.