The U.S. Supreme Court heard arguments on Wednesday over a challenge on free speech grounds to a Texas law that requires pornographic websites to verify the age of users in a case testing the legality of state efforts to keep minors from viewing such material online.

A Texas anti-pornography law is going before the Supreme Court in a collision of free speech rights, regulation of online content and how to protect children.

Texas and 18 other states have recently enacted laws requiring pornography websites to verify the ages of their visitors.