Culture of a country really determines the ethics rules for business. Anyone who has spent time in vastly different cultures can say this.
A friend of mine was in Afghanistan for a while and he told about the practice of gift giving among business owners, clients, government officials and others in Afghanistan. He said that any Westerner would consider this practice bribery, but in Afghanistan, giving gifts is a gesture. It's like a "thank you" and is not considered to be a bad thing.
This obviously has to do with the culture of that country and the traditions and worldviews of people making up that society. When people are doing business in another country, they may have to re-examine ethics rules based on that culture and tradition.