A decision by a federal appeals court this week could have a dramatic impact on the marketing of prescription drugs in America, potentially affecting patient care and everything from TV advertising to future government prosecutions which, in the past, had yielded billions of dollars in settlements, doctors and attorneys said Tuesday.

"This risks taking us back to an era when people could promote snake oil without restrictions – a situation I would hate to see," said Dr. Richard Deyo, a professor of family medicine at Oregon Health and Science University.

However, others say the ruling by a three-judge panel of the Court of Appeals for the Second Circuit in Manhattan is a victory for free speech, one that could become the drug industry equivalent of Citizens United, the 2010 U.S. Supreme Court decision that gave corporations and unions the right to spend unlimited sums on political ads.