As an answer, I am merely clarifying the gemara and tosfos as DoubleAA alluded to..
The gemara's question: Why do we blow shofar during the additional prayer service. We should blow earlier during the morning service based on the idea that the meticulous perform mitzvos as soon as possible (z'rizin makdimim).
The Bavli's Answer: The mishna was learned during the time of a government ban (on blowing the shofar).[Once the time for morning service was over, the guards went home, so they blew during the additional service. Rashi]
The Yerushalmi's answer: Blowing the shofar during the morning service put the Jews in danger as the government thought they were sounding an attack. So they moved it to the additional service so that the gov't would see that they are merely performing a series of religious practices.
Tosfos asks on the Bavli: The mishna was learned during a time of a gov't ban on shofar. So the mishna is an exception. Now that there is no ban, let's re-institute the original law of blowing during the morning service?
Tosfos answers: Since there is a chance that (wherever Jews may roam) the gov't may institute a similar ban, we keep the custom as stated in the mishna and forgo the preference of "z'rizin makdimin".
Tosfos continues: My question does not apply according to the Yerushalmi, since (at least in Tos' time) there is always a danger of the gov't mistaking the shofar for an attack signal.