Katie McDonough argues the trans MMA fighter should be allowed to fight as a woman:

The Unified Rules of MMA clearly outline the weight class divisions that rank fighters, and Fox is part of the featherweight division, along with other women who are between 135 and 145 pounds. And, like the Olympics, many other athletic organizations have rules governing the fair participation of trans athletes. Per NCAA guidelines, a transgender woman can play on a women's team after a year of testosterone suppression therapy. Fox has been hormonally female for a decade now.

Read her column.