How to "unprotect" text in a richTextBox

Question

I have a richTextBox in which I have protected a certain block of text by setting  the richTextBox.SelectionProtected property to "true".  However, it does not appear possible to simply reversed that protection by setting the property to "false".  Microsoft documentation says an attempt to change the protected text can be detected by the "protected" event, whereupon changes can be made, but no example is cited.  Tried using the "cut" method to simply remove it, but the method fails quietly.  Any ideas how this may be accomplished?