Nations ignore the UN
Dictators around the world ignore the UN at will. Even Western nations do not consult the UN when it does not suit them - NATO did not seek UN approval of the attack on Serbia, nor did the US/UK seek UN approval for the invasion of Iraq.
The UN is a unique mixture of realpolitik and idealism. The problem of ad hoc political responses to problems can be reduced by setting a framework of law, causing regimes to find that wrong actions, like genociide and ethnic cleansing, lead inevitably to legal consequences and sanctions targeted on the regime's personnel.