Texas ? A group of families has sued in an attempt to block Gov. Rick Perry’s executive order requiring schoolgirls to be vaccinated against the virus that causes cervical cancer.

The lawsuit challenges Perry’s authority to issue the order and seeks to block any state money from being spent on the vaccine until that question is resolved, said Kenneth Chaiken, the attorney representing the families.

“The school-age girls of Texas are not guinea pigs who may be subjected to medial procedures at the apparent whim of Texas’ governor,” according to the lawsuit, which was filed Thursday in Travis County.

Perry, a Republican, wants to require the vaccine for girls entering sixth grade. It protects against strains of human papapillomavirus, or HPV, that cause most cases of cervical cancer and genital warts.

Supporters of the vaccine requirement say it will help fight a cancer that kills 3,700 American women each year.