For Florida Sen. Marco Rubio, a devout Christian, tweeting out Bible verses to his three million followers has become a routine. Though these tweets regularly receive thousands of likes, one disgruntled nonprofit is claiming they amount to an unconstitutional breach of the separation between church and state.

The Wisconsin-based Freedom From Religion Foundation sent Rubio a letter this month informing him of this alleged violation, requesting the senator either stop tweeting from the Bible or remove “all traces of the public office” from his account.