WINSTON-SALEM, N.C. -- A federal judge's ruling Friday put the Affordable Care Act back into uncertainty  just one day before this year's enrollment deadline.

• Experts say the ruling was a surprise
• Some think the decision will be overturned on appeal
• MORE: Judge in Texas Rules Health Care Overhaul Unconstitutional

A U.S. district court judge in Texas ruled the law's mandate to buy insurance is unconstitutional. Officials rushed to assure the public the ruling won't affect current plans or 2019 coverage.

Spectrum News spoke to an expert  at the Wake Forest University School of Law who says the immediate impact of the ruling will depend on whether or not the judge issues an injunction, but the decision wasn't what he expected.

"This ruling was a big surprise. Even legal experts who are not in favor of the Affordable Care Act thought this challenge would not succeed. Most legal experts think the decision will be overturned on appeal," Wake Forest University professor Mark Hall said.

Despite Republicans' repeated attempts to repeal the Affordable Care Act, many made one of its most popular elements part of their campaign promises this year: coverage of pre-existing conditions.