Dought & clear - Does the consensus of the people of Madinah constitute shar‘i proof?

I have heard that Imam Maalik used to regard the consensus of the
people of Madinah as binding proof. Is this correct? If that is the
case, then is it regarded as binding proof for the entire ummah?
Praise be to Allah.
Imam Maalik (may Allah have mercy on him) was highly focused on the
actions of the people of Madinah and regarded that as proof in the
religion of Allah and thatit was not permissible to go against their
jamaa'ah. He wrote to al-Layth ibn Sa'd (may Allah have mercy on him)
saying:
"The people should follow the example of the people of Madinah. The
Hijrah (migration of the Prophet (blessings and peace of Allah be upon
him)) was to Madinah; in that city Qur'an was revealed, what is halaal
was declared to be halaal and what is haraam was declared to be
haraam. The Messenger of Allah (blessings and peace of Allah be upon
him) lived among them and they were present when Revelation came down.
He commanded them and they obeyed him; heshowed them the way and they
followed him, until Allah took his soul and chose for him that which
is with Him. May peace and blessings and mercy of Allah be upon him.
Then after him came those among his ummahwho most closely followed his
way of those who were appointed to positions of authority after him.
Whatever knowledge they had of what was revealed to him, they
implemented it, and whatever they did not have knowledge of, theyasked
about it and discussed it with others, then they based their
conclusion on the strongest opinion that they were able to reach and
they were very closeto the time of the Prophet (sa). If someone
differed with them, or someone else had stronger and sounder evidence,
they would give up their opinion and follow the other. Then the
Taabi'een cameafter them and followed in their footsteps.
If a certain practice was widely followed in Madinah, I [Imam Maalik]
do not think anyone has the right to differ from it, because ofwhat
they have inherited and their unique situation that no one else can
claim to have. If any other city claimed that this practice originated
in their city, and that they grew up with it and it was the practice
of their predecessors, there could be no certainty that this practice
is sound and they cannot make the same claims as the people of
Madinah.
End quote fromTarteeb al-Madaarikby al-Qaadi 'Iyaad, 1/10
Secondly:
What Imam Maalik (may Allah have mercy on him) was referring to was
the practice of the people of Madinah that they handed down from one
generation to another, and their old practices from the time of the
Sahaabah (may Allah be pleased with him), that were followedby the
people who cameafter them. As for their practices after that time and
their differences with the people of othercities with regard to issues
that could only be worked out on the basis of ijtihaad, Imam Maalik
did not regard that as evidence that it is not permissible to differ
from; rather at best it might support an argument. However, the later
Maalikis differed from him on this matter.
Al-Qaadi 'Abd al-Wahhaab ibn 'Ali al-Maaliki (may Allah have mercy on
him) said:The consensus of the people of Madinah based on what they
narrated from the Prophet (blessings and peace of Allah be upon him)
constitutes proof that it is haraam to go against. As for their
consensus on matters that were worked out bymeans of ijtihaad, there
is a difference of scholarly opinion as to whether it constitutes
evidence. The correct opinion in our view is that we may regard it as
more likely to be correct than other views, but it is not haraam to
differ from it.
End quote fromal-Ma'oona 'ala Madhhab'Aalim al-Madinah, 2/607
Al-Baaji (may Allah have mercy on him) said:
That is because Maalik relied on the views and practices of the people
of Madinah, and regarded them as proof if these practices were based
on narrations, such as the issue of the adhaan, not reciting the
phrase "Bismillah ir-Rahmaan ir-Raheem" out loud in the prayer, the
issue of the saa' (a unit of measurement), not giving zakaah on
vegetables, and other issues that were learned from narrations and
reports and were widelypractised in Madinah in a manner that could not
be hidden, and was transmitted in such a way that it became binding
proof and left no excuse.
End quote fromIhkaam al-Fusool, 1/468
He also said (1/488):
With regard to what they reached by means of ijtihaad and working it
out, there is no difference between the views of the scholars of
Madinah and the views of other scholars, that the strongest view is
that which is based on the strongest evidence. Hence Maalik differed
with the people of Madinah concerning a number of issues.
This is the view of Maalikconcerning this matter, and it is also the
view of some of our companions, such as AbuBakr al-Abhari and others.
It is also the viewof Abu Bakr, Ibn al-Qassaar and Abu Tamaam, and it
is the correct view.
A number of those who followed the Maaliki madhhab but did not examine
this issue fully thought that the consensus of the people of Madinah
constituted proof even in issues that are based on ijtihaad. End
quote.
Shaykh al-Islam (may Allah have mercy on him) said:
The practice of the people of Madinah that was based on
narrationsconstitutes proof according to the consensus of the Muslims,
as Maalik said to Abu Yoosuf, when he asked him about the saa'and the
mudd (units of measurement), and Maalik instructed the people of
Madinah to bring out their saa's, andthey told him that they had
learned this from their predecessors. Maalik said: Do you thinkthey
are lying, O Abu Yoosuf? He said: No, by Allah they are not lying.
And Allah knows best.