Christie claims that the bill would lead to "legal uncertainties" and there would be "legitimate and significant concerns" over security.
"Birth certificates unlock access to many of our nation and state's critical and protected benefits such as passports, driver's licenses, and social services, as well as other important security-dependent allowances," Christie said in a statement announcing the veto. "Accordingly, I remain committed to the principle that efforts to significantly alter State law concerning the issuance of vital records that have the potential to create legal uncertainties should be closely scrutinized and sparingly approved."
This is the second time Christie has 86'd the bill. He vetoed it when it last hit his desk in 2014. He gave the same reasons then as he has this time around.
Currently under New Jersey law, transpeople can only change their birth certificates if they have undergone full gender reassignment surgery. The Birth Certificate Modernization Bill would have allowed transpeople to amend their birth certificates as long as they had proof that they undergoing treatment for a gender transition from a medical professional. The bill had passed without incident in both chambers of New Jersey legislature in June.
Currently, 8 states and Washington D.C. no longer require that trans individuals undergo surgery before they can change their birth certificates.