American Atheists’ most tangible effect on the public sphere lies squarely in the realm of litigation. Since its founding, the group has worked to within the legal system to ensure true separation between church and state. With their efforts, American Atheists has helped the legal community by helping clarify the judicial doctrine known as the Lemon Test. The Lemon Test, established by the Supreme Court in Lemon v. Kurtzman, helps decide what government actions violate the establishment clause of the Constitution.

Lemon Test:

1)  The government’s action must have a secular purpose

2) The government’s action must not have the primary effect of either advancing or inhibiting religion

3) The government’s action must not result in “excessive government entanglement” with religion.

Clearly the language of the Lemon Test is filled with ambiguities. When does the government advance or inhibit religion? What exactly constitutes an “excessive government entanglement” with religion? However flawed the test may seem, the Supreme Court uses this as the standard for all “establishment clause” cases. American Atheists often employs the Lemon Test in their arguments, and by winning cases, sets legal precedent that further clarifies which government actions are unconstitutional. These cases can then be used as precedent for future litigation by private citizens, and as whole, helps reinforce the separation between church and state.

Note: While the appellate court disagreed with American Atheists with regards to the first prong of the Lemon test, they agreed with the group's assertion that the government violated the second prong.