RichHtmlField.AllowInsert property

Gets or sets whether Insert options are shown.

Namespace:  Microsoft.SharePoint.Publishing.WebControls
Assembly:  Microsoft.SharePoint.Publishing (in Microsoft.SharePoint.Publishing.dll)

public bool AllowInsert { get; set; }

Property value

Type: System.Boolean
Specifies whether the insertion of items is enabled.
Returns Boolean.

This restriction only disables the menus and does not force the content to adhere to this restriction.