The new state law took effect when Barbour signed it Monday.
When legislators passed the bill last month, opponents said it was a way to pander to conservatives because Mississippi has had a law since 2002 banning any federal, state or local tax dollars from being used for abortion.
The bill's supporters said they want Mississippi to specify that no public money could pay for abortions once all provisions of a federal health overhaul are set to become law by 2014. Barbour is suing to try to block the federal overhaul.
The bill is Senate Bill 3214.