I see in legal writing the use of double brackets in a quote to indicate part of the quote is deleted, such as: "All work  makes Johnny a very dull boy." I thought the correct way to do this quote would have been "All work ... makes Johnny a very dull boy." Could you tell me when the brackets with no words between them is used correctly? Thanks.
Bryan Garner is maybe the leading prescriptive guru on legal writing. Here is what he says in Legal Writing in Plain English:
On the correct use of brackets:
Use a pair of brackets in a quotation to enclose an editorial comment, correction, explanation, interpolation, substitution, or translation that was not in the original text.
Use a pair of brackets around any character that you change in or add to quoted material.
Use a pair of brackets to show the deletion of part of a word.
Don’t use brackets in place of ellipsis dots when one or more words have been deleted without any replacement language.
On the correct use of ellipsis dots:
Use three ellipsis dots to denote that you have omitted something from a sentence.