Disable/Block Sharepoint Designer 2010

For "disabling SharePoint Designer in 2010" complete the following steps:

1. Open Central Administration 
2. Select Application Management 
3. Select "Manage Web Applications" 
4. Select the desired Web Application for which you want SharePoint Designer disabled, then Under "General Settings" select "SharePoint Designer" as seen below:

Uncheck Sharepoint designer and Click "OK" to save your changes and SharePoint Designer is now blocked/disabled for the Web Application.