Michael Newdow's faith is being tested.
The atheist has had argued that government references to God are unconstitutional and infringe on his religious beliefs.
He was appealing a decision last March by the 9th Circuit U.S. Court of Appeals in San Francisco who said the phrase is ceremonial and patriotic and "has nothing whatsoever to do with the establishment of religion."
Monday the Supreme Court refused to hear the appeal.
Newdow has also sued to ban prayer at presidential inaugurations and to ban the phrase "under God" from the Pledge of Allegiance. He has never won a court battle.