Hi

In order to avoid a purchase user from affecting Warehouses, we need to control the access rights of that particular user through:-

• Go to Settings> Users>Groups. Here we have two groups belonging to Warehouses namely Warehouse Manager and Warehouse User. We need to remove the Purchase User from these groups and automatically that user would not be able to access any matter associated with Warehouses.

• This is because user access rights in Odoo are controlled through Groups

Hope this helps

 Cheers

Hello

To limit your purchase user you can create record rule. Below link will help you to create record rule.

https://www.odoo.com/forum/help-1/question/how-to-use-access-rights-and-record-rules-40960

http://stackoverflow.com/questions/29511874/how-to-set-record-rules-in-odoo