Hi momonono:
Thanks for reaching out to Microsoft Q&A.
Do you mean the supplier has to be denied uploading data into azure sql database? for this either you can create a separate login for the user to use in his data factory pipeline and set that login with a restricted access inside the database.
(or)
You can try exploring the custom roles in adf. The below link is one example where the custom role was created to restrict users from creating/deleting the linked services, but you can modify to suit your requirement.
and this one...
https://davidalzamendi.com/role-reader/
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