In 1927 the rabbi of a Syrian-Jewish congregation in Buenos Aires banned all conversions to Judaism in Argentina forever ("ad kol yemei olam"). The ban is still in effect today. Candidates for conversion in Argentina must have it done elsewhere.
(1) On what grounds can rabbis make such pronouncements, tying the hands of all future rabbis, even if conditions should change?
(2) What is the practical value of such a ban, if candidates can get converted outside the country?