This was said in a pretrial conference in response to an unusual procedural request from the opposition. It is a nice mash up of “on dangerous (shaky) ground” (a proposal on an unstable or questionable foundation), “treading lightly (or carefully)” (cautious), and “venturing in uncharted waters” (going into unfamiliar or unclear situations). The latter seems particularly in the speaker’s mind considering the context. This malaphor is very similar to a recent one I posted: “I’m treading in uncharted waters”. https://malaphors.com/2016/08/03/im-treading-in-uncharted-waters/
A tip of the gavel to Tom Justice who heard this one and passed it on!
If you liked this mixed metaphor you will love the book He Smokes Like a Fish and other Malaphors. It’s available on Amazon for the cheap price of 6.99!