In some cases it is not recommended to allow editors to change the layout of a frontpage. For this reason you are able to tailor the editors rights and permissions and as such limit their layout editing abilities. This feature is based on the eZ Flow policy, which should by default be added to the "editor" role.

 To limit the permissions, log in to the Administration Interface and go to the "Roles and Policies" link under your User Accounts-tab.
 

Select the role you wish to adjust or create a new one based on the default editor role, the latter is recommended. Locate the ez Flow policy, remove it and then add a new eZ Flow policy. This sounds silly but the default eZ Flow policy cannot be edited so this detour is necessary. In the new eZ Flow policy only grant access to the "Call" and "Edit" functions.

Click "ok" and from now on users based on this role will no longer be able to modify the front page layout.