A Gezerah is a Rabbinical prohibition. Any Rabbinical court can make a
Gezerah for the people who accept its jurisdiction. If the court was in
the time of the Talmud (or earlier), the Gezerah would be mentioned in
the Talmud, and would usually be universally binding on Orthodox Jews;
this would not always be the case for a Gezerah made by a later court.
A Gezerah is a prohibition, and a Takanah is a positive ordinance.
The term "Gezerah" is also used for Divine decrees. The term "binding"
isn't appropriate for them; they are things that are destined to happen.
But repentance often annuls a Divine Gezerah.
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