No there is no rule that Pak should not get nuke support...but of all why from China...a peacefull country as it professes to neighbour's enemy. China signatory of NPT covertly transferred it to Pak against the NPT. US on the contrary is still thinking twice whether to offer CIVILIAN nuke technology for energy purposes to India? And it is common knowledge why and against whom Indians nuclear tests were directed. So That should answer the umpteen number of your questions.
