Well, Putin is right in a way that the proposal to change the Constitution really seems rather, uh, strange. Doesn't the British Premier realize that countries usually don't change their laws because another country told them so? And I honestly cannot understand why the British officials are hiding some proofs of Lugovoi's guilt from Russia. Doesn't it seem counterintuitive?
But, having said that...
I find it hard to understand why Russian "ruling classes" (if they hadn't ordered to kill Litvinenko themselves, of course) are stubbornly refusing to cooperate with the Brits in any way. "Lugovoi will remain in Russia - and that's all we say! And it is not our business if he's accused of murder!"
While there are many different way of finding a way of suing Lugovoy that will suit Britain and not violate the Russian constitution, I am sure. Russia can, um, ask Lugovoi to come to Britain on his own will. Russia has a piese of territory in London - it is called the Russian Embassy. Maybe investigation can take place there? Maybe Lugovoi can be judged in Russia - but in the presence of British experts, and if they find signs of foul play on Russia's part, them it will be proven that Russia hides something it should not.
It seems that it is in Russia's best interests to cooperate - that it should be eager to fing was it really Lugovoi to killed Litvinenko - after all, having a murderer in the country is not something unworthy of attention. But, apparently, Russian ruling classes do not think so... Hm? Any ideas why they don't think so?
Althrough, I repeat, the British position is a bit illogical too...