A world constitution for your generations

Usually, Chazal require expressions like “world law” to mean that a certain law always applies, even where it should have been repealed (in the Kedshim, the word “huqa” is required to mean that it is a hindrance). The assumption is that the entire Torah does not change or abrogate, but there are sometimes conditions in the law in the absence of which the law is supposed to be abrogated for halachic reasons. Here a word like “constitution” can mean not to abrogate the law. Or there is a reason to abrogate the law for some reason and therefore this word is required to mean not to abrogate. An example of this is that the process of conversion requires the offering of blood (a sacrifice). Apparently, according to this, when the Temple is empty, it is impossible to convert. The Gemara in Kiratot 9a makes this difficult: But from now on, as for this offering, we will not accept foreigners, said Rav Acha bar Yaakov. And if a foreigner who is among you should live with you, etc. It requires the word “for your generations” to mean that when it is impossible to sacrifice, one can convert without a sacrifice.