Is there any way to prevent Lead Assignment Rules from triggering when I update a Lead through the REST API? I see this happen through the C# libraries and even just using Postman.

Even if I just change a name field, it re-runs the Lead Assignment Rules and re-assigns the lead owner :(

I see this was posted as a problem with 0 replies in 2012 too:

https://developer.salesforce.com/forums?id=906F00000009ABoIAM

Hello, 

Over the past month my Salesforce org has been having Marketo/Saleforce duplicate lead sync problem. For certian leads at random times an action/trigger is duplicating leads as many as 15 times that getting synced over from Marketo. I was able to monitor the action that was setting off the duplicates (Screen shot below).  Has anyone ever had this problem before? If so, how can I stop this from happening? 

What is really strange ....is Salesforce seems to be reading the leads as web to lead. 


Please see action in the screenshot below: