Update May 20, afternoon: McMaster has softened his stance. Get the latest.

First reporting:

Craigslist appears to be quite serious when they say they feel they're being unfairly and unjustly targeted by South Carolina's Attorney General: The online classified giant has filed a lawsuit.

Read more stories on this subject in our Craigslist topic page.Here's the details from Craigslist's blog post:

craigslist has filed suit against SC AG Henry McMaster in federal court in South Carolina, seeking declaratory relief and a restraining order with respect to criminal charges he has repeatedly threatened against craigslist and its executives.

...

Mr McMaster’s repeated threats of criminal prosecution should we refuse to shut down craigslist for South Carolina have left us little choice but to seek declaratory relief before the court.

Keep reading at their blog.

If you're just joining us, S.C. Attorney General Henry McMaster has said his office will move forward with a criminal investigation and potential prosecution of Craigslist. You can catch up with past news and the latest on our Craigslist topic page.

Update: For curious readers, here's a copy of Craigslist's legal filling.