Possessives

I am having difficulty in determining whether or not an apostrophe needs insertion after the word “Investigators” in the following Act that discusses licensing private investigators:- Private Investigators Licensing Act 2012I didn’t think the apostrophe was necessary. It isn’t a reference to each investigator’s license that will be issued, but generally the process of being licensed as a private investigator. I don’t understand the need for the apostrophe in this case.However in the following case, I would think that the apostrophe is required:- Teachers’ Superannuation Act 2001Could someone please assist me in understanding this? Thank you.