I recommend that you do something similar to that like henchmen and add a race pre-req for your tech. I'm not sure exactly how the tech tree works, but this will at least have only your race be able to use your tech, similarly you can add a faction requirement as well.

Well I just got it too work. It was a bloody typo of all things. I feel like a tard now, but thanks for the reply people. I'm mean I havent throroghly tested it yet. I just noticed the typo, saved, jumped into a new game and bang, the associated techs were gone.

I'll remember that next time, lol.

Just a follow up. Tested custom faction for many hours, all is well, works as intended. I was able to block all techs in the Mounted line, and Archery line. No worry, I'm compensating the faction in other ways to ammend this apparent nerf. They still can recruit and design Magi. 

Another thing I learned, watch your internal names.

I could not even begin to guess the number of hours I've spent debugging code because of a small typo!  You're no tard!