Related על כתובות 51:3

There are 2 grounds for presumption of being a priest in Eretz Yisrael: doing the priestly blessing and taking one's portion from the threshing floor. But in Suria and until the place that the Rosh Hodesh heralds arrive, doing the priestly blessing [is a ground for presumption] but not taking one's portion from the threshing floor. Bavel is like Suria. Rabbi Shimon ben Lazar says: Also in Alexandria originally, since there was a court there. Rabban Shimon ben Gamliel says: Just as terumah is a ground for presumption for being a priest when one takes it from the threshing floor, so too is first tithe a ground for presumption for being a Levite when one takes it from the threshing floor. One who takes his portion in a court does not have grounds for presumption to being a priest.