If you are a Distinguished Developer you can block users from downloading your content from your Account Settings page. Below are screenshots that explaining the process.
- Click on your name and go to "Account Settings" (image)
Click on "Download Restrictions" and enter in the username(s) of the users you wish to block (image)
- You can also remove users at anytime.
Interested in becoming a Distinguished Developer? Click here for more information on the process for becoming one.