This text says that, when Hanina the nephew of R' Yehoshua went to Babylonia (apparently after the crushing of the Bar Kochba rebellion), he made decisions regarding declaring Rosh Hodesh and intercalating the year, and that the authorities in the Land of Israel sent two scholars after him. They told Hanina, disingenuously, that they were coming to learn Torah from him. He then extolled them to the Jewish community in Babylonia, calling them great scholars. Then they began contradicting him -- he would declare an object impure and they would declare it pure; he would forbid an action and they would permit it. Frustrated, and embarrassed, he proclaimed that they were good-for-nothings, but they pointed out that he had already vouched for them and could not undo that. He then asked why they kept contradicting his rulings.
Their response is that it is because he had been making calendrical decisions outside the Land of Israel. This response is fascinating -- they do not indicate in any way that his decisions about ritual purity, or on prohibited actions, were wrong. They apparently set about systematically overruling all of his decisions on all sorts of halachic questions, even though, it seems, he was right in those decisions. Preserving the central authority to set the calendar was considered so important that it not only warranted sending two scholars on a trip to Babylonia, and not only warranted threatening Hanina and the entire Babylonian Jewish community with excommunication if they didn't fall in line. It also warranted actually making wrong legal decisions, telling people that they could use objects that were really impure, and telling people that they could perform actions that were really forbidden, just in order to undermine Hanina's authority.