Interesting question. I think as Traditional Owners they are entitled to catch, keep or kill anything they want on their homelands......the problem comes with passing it on to you. Suprising that they want to go and catch them for you...most aboriginal people are really frightened of snakes...and I'm not sure what condition they would arrive in!
I wonder what Parks will have to say about this. There was a very eccentric woman up there many years ago who used to spend a bit of time hunting with Bining (Aboriginal people) in western Arnhem Land. She was reported one day for hunting Water Pythons with them and Parks intended to push for charges, The locals responded by giving her a Skin name and making her part of their extended family...hence avoiding any legal action........well anyhow that's how she related the story to me!
Would be even more interesting if they intend to supply you with things like Oenpelli Pythons!