Why would he need any lines then?

The quote is indeed about the law being a nose of wax, to borrow an old English phrase, and how with sympathetic enough courts almost any decision could be upheld. But it's nothing new, precisely the same crime can yield drastically different judgements depending on e.g. the defensive attorney's experience.

He was powerful enough to hang someone on a flimsy excuse, but not so powerful that he did not need a flimsy excuse. Right in that sweet spot.