Unsigning the Covenant

On Monday of this week, I ran an item on this blog about the date of signature of the International Covenant on Civil and Political Rights by China. Yesterday, the United Nations changed the date of signature of China on its treaty database. The entry now reads 5 October 1998, which is the date of signature by the People’s Republic of China. There is a footnote indicating: ‘Signed on behalf of the Republic of China on 5 October 1967.’ I'm glad to see that they are reading the blog!
Many of us laughed in 2002 when the Bush administration (and Israel) purported to ‘unsign’ the Rome Statute. But that seems to be what the Secretary-General of the United Nations has done with respect to the ‘Republic of China’.
Withouit wanting to be overly technical, one could argue that the People's Republic of China was bound as signatory to observe certain obligations (art. 18 of the Vienna Convention on the Law of Treaties) because when it took the Chinese seat in the United Nations it in a sense inherited the rights and obligations associated with China, like membership in the Security Council, but also duties as a signatory of the Covenant. The Secretary-General now says China wasn't a signatory of the Covenant from 1971, when it joined the United Nations, until 1998. In effect, then, China's human rights obligations have been reduced. I think this is inconsistent with the general view that a State that succeeds to another is bound by the existing human rights obligations. Admittedly, the China case is not a classic one of State succession. Still, we shouldn't be reducing the application of the Covenant to a State, as the Secretary-General seems to have done. Can a State escape from its obligations by 'unsigning' a treaty and then resigning it at a later date?