"It is legally bound, under higher laws which it has acceded to, as part of its United Nations obligations, to accept the transfer of political refugees to the country which granted asylum,".
Makes me wonder what those higher laws actually are. But if he feels this way; why not start a prosecution?
I think he's totally off though. Because if you look closely you'll see that there still is no "official" system in place which regulates the use of immunity. For example; because of the immunity of ambassadors and their cars they normally also don't have to worry about parking violations. As a result plenty of diplomats basically allow their cars to be placed "where possible", even if it's officially not allowed.
Yet there are also many countries which don't tolerate such behaviour and demand that their own embassy personal pays up for their own traffic tickets. And there are also host countries which use alternative means to enforce the law. In Holland it's not uncommon for a diplomatic car to get towed away. They can't search it but it seems they can move it out of the way.
Or what to think about embassies which hire personal from the host country but immediately make it clear that they can't count on immunity because they're not citizens of the main country?
A small example, but one which clearly shows that there currently is no specific ruling in these matters. Some countries are very strict with upholding diplomatic relationships (not paying for traffic fines) whereas others couldn't care less about "pesky details".
As such, I think Mr. Assange is doing some wishful thinking here, but he seems to be completely off.