For those planning to use an officiant ordained online, Tennessee has recently been added to the list of states in which this is not permitted. The intent seems to have been to make same-sex marriage more difficult, but of course it also applies to opposite-sex marriages.
A court has blocked the enforcement of the law for now, but couples considering using an Internet ordained officiant in the future should be aware of the risk.
Those using Internet ordained officiants in other states may want to review this article discussing the legalities of the situation: