So, we will have problems in the custom if we bought an ivory´s or bekko’s bachi? … in the other hand, they are small items. Anyone knows? 
Paco, I know a little, but it’s enough to make this a rather long answer. 
Of course, Customs is usually looking for people who are doing illegal things on a large scale. However, under the law, even for a small item, if the material is contraband (illegal), then it is illegal to buy/sell/transport it across borders. If one is caught with it on them or caught importing it (eg, because your parcel got opened by Customs inspectors), Customs won’t care about size. Illegal is illegal, and ivory and bekko/tortoiseshell products are two of many restricted materials.
What products are forbidden, which and how certain materials/plants, etc. can be bought, sold and traded is controlled by the Convention on International Trade of Endangered Species of Flora and Fauna. It is usually just called CITES, pronounced site-eeze. Here is their (complicated :-D) website - www.cites.org. And here is a shorter outline of CITES - http://en.wikipedia.org/wiki/CITES. About ~175 countries have signed CITES treaties and agreements. The member countries then enforce CITES’s rules by laws that they make in their own country. So you need to check your country’s laws to see what could happen if you were caught.
For an example, here is the situation in Canada. CITES is handled through the Wild Animal and Plant Protection & Regulation of International & Interprovincial Trade Act (WAPPRIITA). Canada’s Department of the Environment is responsible for enforcing CITES rules through that Act. Individuals convicted under WAPPRIITA can face a fine of up to $150,000 or five years in prison. Corporations can face fines of up to $300,000. I think fines and penalties around the world are probably similar to those…
Of course, many people still bring in small items that are restricted. Sometimes they don’t even know that a product is illegal or partially restricted in the first place. (If you look at the lists of them on CITES’s website, they are very l-o-n-g and detailed!). However, in most countries, ignorance of the law is not a valid defence. There is always the risk of getting caught by a random search, by “sniffer” dogs at an airport (I was surprised to find Toronto’s airport using dogs starting about two years ago…), etc. So everybody has to decide for themselves if it’s worth it to put that item (eg. ivory bachi, bekko koma, hair clip, etc.) in their luggage or to have it shipped to them. It probably turns out okay most of the time, but you just never know… And as long as people do keep bringing in that “one small item”, the animals will continue to be killed and/or become extinct - something else to keep in mind, because it was the reason for the restrictions in the first place.