Even if you're not a unit of interest, you get implanted with an "identification bolt" which contains detailed personal information on your body capabilities and personality, and can be read easily by any TransTech even without your permission.
And even if you're allowed to leave Axiom Nexus (Eventually. Once you work through all the proper paperwork and fees.), the TransTechs have full control over where they send you. Which can involve "an approved alternate reality" instead of your real home universe.
In "Withered Hope", we are given a glimpse of General Demolishor's alternate mode. Considering the character, it's probably supposed to be some kind of tank, but it really doesn't look like much besides a horrible metallic monstrosity◊.
The fact that, as oppressive as the TransTechs' security is for anyone they deem different, it's almost arguably justified, since:
"There were things that defied known science that lived within the void of transwarp, creatures of pure malice that could not exist within the material plane. It was virtually impossible that the second stream contained any of these extraplanar creatures, but their taint could affect material beings; such 'avatars' did rarely appear, and were capable of incredible destruction for the unwary and unprepared."