Raavad and Rambam on when a law that a decree but not from the Torah is nullified.

I have no Rambam or any way to look this up. But if I recall correctly the Raavad puts his comment about R. Yochanan and the first fruits on halacha 3 and his comment about when the law is accepted throughout all Israel in halacha 2. [That is in laws of ממרים ]

From what I recall Halacha 2 says when the reason no longer applies for a  גזירה or תקנה or a מנהג that was instituted by the great beit din in Jerusalem and has been accepted by all Israel, then another beit din can nullify it if it is greater in wisdom and numbers. But how is it possible to be greater in number when the number is already set to be 71, n more or less. The Ramabm answers this refers to teh number of the sage of Israel that agree with the Beit Din. [The Rambam in all three halachot deals only with the great beit did does not enter into the question of what about a lesser beit din or a beit di today with no semicha].
On this halacha I think the Raavad say No, but once it has been accepted by all Israel even a beit din with great numbers and wisdom can not nullify it.

Then in halacha 3 the Rambam writes a law that was made as a סייג לתורה then even  beit din with greater wisdom and numbers can not nullify it. On that the Raavad brings that R. Yochanan nullified the law to adorn the streets of Jerusalem with the first fruits even though he was not as great as the Beit Din that made the law.

What seems to come out from this to the  Raavad is that if the law has been accepted by all Israel then even though the reason no longer applies, no beit did can nullify it, and if it was not accepted by all Israel then even a smaller beit din can nullify it. To the Raavad everything depends onif it has been accpetd by all israel.