SharePoint Designer provides a great deal of customizing power to its users. In some environments, particularly in an enterprise, giving all users access to this level of power may not be appropriate. To address this, SharePoint allows system administrators and site owners to configure different levels of access for users of SharePoint Designer.
First and foremost in the governance of SharePoint Designer is the proper application of regular security roles to a SharePoint site. Quite simply, even if a user downloads and installs SharePoint Designer, he cannot use it to make any changes to a site he would not otherwise be permitted to make. For example, a typical user in the Member role cannot change themes or master pages, or modify the schema of a list or library. SharePoint Designer would not suddenly enable him to do so. A user would need to be in (for example) the Web Designer or Administrator role on the site in order to make such changes, regardless of any tool he has installed.
In SharePoint 2010, you also have the settings for directly managing the use of SharePoint Designer, irrespective of the regular security of a site. These settings allow or prevent access to certain features by users of SharePoint Designer.
The SharePoint Designer controls screen is shown below
This page is accessible at different levels within SharePoint, depending upon the scope over which control is to be exerted. You can set these options at the web application or site collection level. If SharePoint Designer or one of its features is blocked at the web application level, it cannot be overridden by a site collection owner. Nevertheless, a site collection owner can invoke tighter restrictions than are set at the web application.
Note: Restrictions implemented at the site collection level impact most users, but do not apply to the site collection administrators themselves.
Regardless of which method or methods you use to restrict SharePoint Designer, your choices will be reflected in the experience presented to the users. The user interface of SharePoint Designer is security trimmed. This means that users are only shown the functions that they have the right to see or control. This figure shows a Site Objects list with all the SharePoint Designer options enabled (the default state).
Compare to the figure below, which is the same site with the options disabled.
Observe that access to the Master Pages gallery and direct access to the site files are not visible in the restricted site. Other elements throughout the user interface, such as context menus, are similarly trimmed.