United Nations - why do we bother?

The UN torture investigator has been denied entry to Zimbabwe, despite being invited by the country's Prime Minister Morgan Tsvangirai, the UN says.

Manfred Nowak said he was stopped by immigration officials after landing at Harare airport on Wednesday evening.

Read the rest of the story at: http://news.bbc.co.uk/1/hi/world/africa/8329984.stm

Elsewhere on the blog we read about the UN bringing to account other world leaders who have committed 'crimes against humanity'. Yet here is a story that reveals the problems the UN faces; the reality is unless the major world powers actually want to support the UN it is the equivalent of a 'toothless watchdog', just like it's predecessor The League of Nations. As you know I am not cynical in any way, yet how can the UN justify intervention in the affairs of the former Yugoslavia, Iraq and Afghanistan, yet not intervene in Zimbabwe.

What do you think? It would be useful to get some comments on this - is the UN just another tool for US foreign policy objectives?