Among the healthcare law’s most popular features is a provision barring insurance companies from rejecting people with pre-existing medical conditions. A new government study out today estimates that as many 129 million Americans under the age of 65 have medical conditions that would trigger either rejections or price hikes from insurance companies. According to the study, one-fifth to one-half of the non-elderly in the United States have ailments that would limit their ability to obtain insurance if the law is repealed. The provision is set to take effect in 2014; a measure barring the rejection of insurance to children with pre-existing conditions came into effect last year.