I_am_snake, I am not familiar with the Territory's specific laws in this regard. You can be assured is that each state or territory will have legislation governing it, as Geckphotographer pointed out. To take an example, freeze dried Thorny Devils would make a very popular momento of a trip to the NT. To say I found it dead might wash with one individual but if someone was dealing in multiples of 10...
So there is good reason for prohibitive legislation. However, I warrant that every country primary school and high school will have a bottled collection of roadkills and similarly collected dead specimens along with skulls and bones. The same is likely to be true of any local naturalists clubs. Despite the potential illegalities, to the best of my knowledge no educational institution or environmental oriented group have ever been prosecuted in any state or territory for such offences. The authorities do seen to acknowledge that that bottled specimens, irrespective of their condition, are not particularly saleable items and in the context of providing an educational resource they are happy to turn a blind eye.
While that is my perception of how the system tends to operate it remains your responsibility Dan to do the homework needed to bring you up to scratch on the local legislation and how it is implemented. I would suggest you make enquiries as to want is a required to legalise collection and preservation of specimens under your authorities. That will put it beyond doubt.
Blue