A conservative group representing more than 50 Illinois parents challenged the Obama administration’s aggressive stance on letting transgender students use the bathrooms of their choice Wednesday — the same day the Justice Department warned North Carolina that a law requiring transgender people to use bathrooms that align with their gender at birth violates the Civil Rights Act.The pair of developments seemed poised to increase the political pressure surrounding the administration's interpretation of Title IX of the Civil Rights Act, which prohibits discrimination in education based on sex, and signals that a drawn-out legal battle — possibly going as far as the Supreme Court — could be in store.