Sounds like your Dad and friends were investigating a change in status. Here in the US, I have stumbled on to information about removing the burden of being a "US CITIZEN" and returning to the pre-Civil War status of State National. It is here that taxation ceases and freedom truly begins. I think you are correct in stating they cannot tax a man/woman, but the legal terminology will always bite you if not well-versed on the topic- i.e. they can tax a person. In law this is a corporation. When your birth certificate was recorded a franchise was created in your name and it is represented with all capital letters (just look at your COLB or drivers license).
Here is a good presentation to point you in the right direction: http://www.blogtalkradio.com/wbnslope/2016/08/13/ken-cousens-on-correcting-our-death-status-to-step-into-the-land-of-the-living
Yes that is also part of it. The all caps thing. That makes since about returning to before or changing status. It would also mean getting no gov benefits.