The Freedom from Religion Foundation is suing to take away a tax break from churches.
The Wisconsin-based atheist group says it's unfair that churches are allowed to give pastors tax-free housing.
Upset that other non profit organizations such as theirs don't get the same tax exemption, they want the government to ban the allowance for ministries.
"We think the law is rotten at the core," The Tennessean quoted co-president Annie Laurie Gaylor. "It is not constitutional, it is not fair, and it is not necessary."
However, supporters of the exemption have noted that a similar attempt failed back in 2002.
"I don't think this lawsuit is going anywhere," said Dan Busby of the Evangelical Council for Financial Accountability. "Both houses of Congress don't want to touch this."
The Justice Department could respond to the lawsuit by the end of the month.