How to Prevent Suppliers from Posting into a Campaign
This article outlines how you can prevent suppliers from posting into a specific campaign - it also shows how you can prevent a supplier from posting leads into all campaigns at once at the account level.
Campaign Level
Disabling a Supplier at Campaign level will prevent them from posting into a specific Campaign but will not stop them from posting into any other Campaigns.
The video below explains how this can be performed:

Account Level
If you don't want your Supplier posting into any of your Campaigns, you can disable them at an account level.
The video below explains how this can be performed:

Supplier Responses
If a Supplier tries to post into your Campaign while disabled, they will receive a rejection message. However, this differs based on how they are disabled. Examples below:
Campaign level:
Account level:
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