At the cost of it being really obvious where you are.
However the bigger draw is probably high bandwidth two way communication globally. No need for an obvious route as you can use GPS to get near US waters before turning it on, while still being in control of location of delivery or even meet up with it on the open ocean.
Sending the position only requires a few bits, let's say 48. A position update requires even less, depending on how far it could have travelled since the last known position. At such low data rates you could hide the transmission quite effectively.
As a once off it’s not going to be investigated, start making regular trips and people are going to start looking for such signals. Short bursts strong enough to detected many hundreds of miles away inherently need to be fairly strong making them standout from the background noise for close receivers. You can similarly triangulate based on signal strength given some ocean ships or even cheap buoys.
Starlink needs to be detectable by satellites, but you can almost completely block the signal going in other directions.
SpaceX might already be sharing it’s data with coastguards though.
I also wonder if you could have a visible surface vessel (e.g. fishing boat) which acts as a navigation beacon for the sub. Sub can just follow the beacon without any active communication of its own. If enforcement appears, sub will destructively sink to avoid revealing the operation.
