At Snyder's son's funeral, members of the Westboro Baptist Church of Topeka, Kan. carried signs that read "Thank God for Dead Soldiers" and "God Hates the USA".
Snyder won an $11 million verdict against the church for intentional infliction of emotional distress, and other claims. A judge reduced the award to $5 million before the federal appeals court in Virginia threw out the verdict altogether, citing the church's First Amendment rights.
Justice Ruth Bader Ginsburg said the question is whether the First Amendment must tolerate "exploiting this bereaved family."
Church members claim they have the right to say what they want, saying that U.S. deaths in Afghanistan and Iraq are punishment for Americans' immorality.
The case has sparked outrage across the nation and pits privacy rights against free speech.
The Associated Press contributed to this report.