By The Associated Press

U.S. District Judge Reed O'Connor, who ruled the Affordable Care Act "invalid" Friday, is no stranger to the conservative resistance to Obama administration policies.

O'Connor, 53, is a former state and federal prosecutor who was nominated to the federal bench in 2007 by President George W. Bush. He has been active in the Federalist Society, which describes itself as "a group of conservatives and libertarians interested in the current state of the legal order."

In 2014, the Fort Worth, Texas-based judge upheld the constitutionality of an Arlington, Texas, ordinance that bars people from handing out printed material at busy intersections and roads. The lawsuit had been brought by a gun-rights group called Open Carry Tarrant County. Although he upheld the ordinance, O'Connor ordered the city to pay the group's coordinator $42,251 in damages.

That same year, he sentenced a man to more than 15 years in federal prison for kidnapping and severely beating a gay man he met through an online service, concluding the assailant kidnapped the man because of his sexual orientation.

In 2016, though, he blocked a federal directive that required public schools to let transgender students use bathrooms consistent with their gender identity. He ruled that Title IX, which the Obama administration cited in support of the directive, "is not ambiguous" about sex being defined as "the biological and anatomical differences between male and female students as determined at their birth."

Also in 2016, he struck down new U.S. Health and Human Services regulations that advised that certain forms of transgender discrimination by doctors, hospitals and insurers violated the Affordable Care Act. He declared that the rules placed "substantial pressure on Plaintiffs to perform and cover (gender) transition and abortion procedures." A coalition of religious medical organizations said the rules could force doctors to help with gender transition contrary to their religious beliefs or medical judgment.