It seems from the daf that the zavim, mitzarot, and baalei nidot are allowed to learn torah, but the baalei keri not.
Although I can't recall the place, I recall having learned the maaseh of a talmud who would not learn on account of keri. His rav answered him, that "divrei torah ain ma'cablin tumah," to the effect that he should not abstain. What is the difference?
H. David Levine, Roanoke, VA
David, the Gemara you are thinking of is in Berachos 22a, and it was Rebbi Yehudah ben Beseira who told his Talmid to continue learning. The Masores ha'Shas on the margin of the Gemara there refers us to Tosfos to Bava Kama 82b, who writes that the Halachah follows Rebbi Yehudah ben Beseira.
It was Ezra ha'Sofer who made the original decree that a Ba'al Keri should not learn Torah, but afterwards this decree was retracted, because they saw that most people could not manage with the requirement to go to the Mikvah often in order to be able to learn Torah. Rebbi Yehudah ben Beseira reverted the Halacha to the Torah practice before Ezra's decree. (See Shulchan Aruch OC 88:1, and Mishneh Berurah #2.)
Kol Tuv,
Dovid Bloom