“Cis” can be a noun or prefix, meaning “on the same side [as]” or “on this side [of]”, with several derived usages:
Trans-Atlantic versus cis-Atlantic, trans-Mississippi versus cis-Mississippi.
In other words, it's a really, really obscure prefix, almost never used, and the writer is just having fun with it and the term transgendered.
The term cis-gendered is actually part of the wording of the legislation. My background in genetics leads me to believe that cis-gendered are those individuals who have been born with both male and female sexual organs.