According to ICC's player eligibility regulations released in 2018 (and amended in 2021), trans women wishing to play women's international cricket must demonstrate "the concentration of testosterone in her serum has been less than 5 nmol/L1 continuously for a period of at least 12 months, and that she is ready, willing and able to continue to keep it below that level for so long as she continues to compete".
It further states that a trans cricketer must "provide a written and signed declaration, in a form of satisfactory to the designated medical officer, that her gender identity is female".
On allowing McGahey to be the first transgender to play international cricket, the ICC said in a statement: "We can confirm that Danielle went through the process as required under the ICC's player eligibility regulations and as a result, has been deemed eligible to participate in international women's cricket on the basis that she satisfies the MTF transgender eligibility criteria."