The Internal Revenue Service is arguing that it has the right to read Americans' email without a search warrant.
IRS lawyers have written in official documents that Americans don't have privacy rights in their email or other online messages.
The American Civil Liberties Union obtained those IRS documents and it believes that position is at odds with the Fourth Amendment of the Constitution.
That amendment says people are free from unreasonable searches and seizures.
A federal court ruled in 2010 that Americans do have a right to privacy in their email, but the IRS has not changed its policies about searching emails without a warrant.