Trophy hunting of Lions

In lay-man terms Trophy hunting is like "raaping inside prison cell, protected by police". Here is some in depth news...

BBC
http://news.bbc.co.uk/earth/hi/earth_news/newsid_8993000/8993557.stm
Tanzania currently allows about 500 lions and 400 leopards per year to be killed for sport across a total area of 300,000km². ....The idea is to fund conservation.

Evidence comes from a survey of lion harvests in the country between 1996 and 2008 which found that the number of lions hunted fell by 50%.

Lion imports
http://www.ouramazingplanet.com/endangered-african-lions-protection-110302-1180/
From 1998 through 2008, at least 7,445 wild lions were traded internationally, and at least 4,021 of them were brought to the United States, including more than 3,600 for recreational trophy hunting purposes.

US must be paying for conservation of wild-life in Africa. Why not just impose ban on US citizens importing Trophy lions in to country?. Ban would be more effective. On the same lines, we should also stop selling arms to dictators and stop paying for spreading democracy.