Gavra @ Work:
The Rambam you quoted is referring to a Beis Din situation; the question asked here was regarding a kashrus shaila to a posek. If you “witnessed” the kitchen staff in your yeshiva bringing in tarfus, and asked (say) the Rema a shaila (as he was the Rov of the town), and the heilige Rema paskened unquestionably that it is kosher — and furthermore the Rema ordered you to eat it (perhaps so the other talmidim don’t refuse to eat it based on your eidus), what would you do? [Remember the Rema is issuing a psak. This was the question posed on this thread.]
It would seem to be similar to the Gemorah in Rosh Hashana 25a where Rabban Gamlier forced Rabbi Yehoshua to walk to him with his wallet and stick, on the day he calculated to be Yom Kippur.