יא

אִם הִטִּילוּ הַקָּהָל חֵרֶם, שֶׁלֹּא יִשְׁחֹט אֶלָּא טַבָּח יָדוּעַ, וְשָׁחַט אַחֵר, יֵשׁ אוֹמְרִים שֶׁשְּׁחִיטָתוֹ אֲסוּרָה.

 

Seif 11

 

If a community instituted a pronouncement  that only a specific butcher would be allowed to slaughter, and another butcher goes ahead and slaughters, (regarding what he slaughtered) There are those who say that what he slaughtered is forbidden.