Bryan Barton has been cleared in the supposed case of illegal detention:

..."The county attorney's office reviewed all available evidence, that indicates that there was no forcible detention, . . . and no charges are pending," said Carol Capas of the Cochise County Sheriff's Department.

The sheriff's department, Mexican Consul Miguel Escobar and the U.S. Border Patrol also agreed the 26-year-old man was not detained, said Capas and Border Patrol spokeswoman Andrea Zortman...

The Washington Times has more in "Protesters cleared after review":

"[The alleged illegal alien] thanked us about a dozen times," and didn't complain until after he was in custody, said Mr. Barton... Minuteman organizer James T. Gilchrist yesterday said Mr. Barton was guilty of a "benevolent act by a naive member." He said Mr. Barton resigned effective today...

Yesterday the ACLU of Arizona issued a press release entitled "ACLU of Arizona Denounces Unlawful Imprisonment of Immigrant by Minuteman Volunteer":

The American Civil Liberties Union today condemned the actions of volunteers with a controversial citizen border patrol program known as the "Minuteman Project" for reportedly holding an individual against his will and photographing him holding a t-shirt with a mocking slogan...

Despite claims on the Minuteman Project website that volunteers would only spot and report individuals they suspected were violating a federal law, the unlawful imprisonment occurred during the first few days of the month-long project...

As reported today by The Associated Press, Border Patrol agents called in deputies from the Cochise County Sheriff's office on Wednesday afternoon to report that an immigrant was detained by three men who identified themselves as Minuteman volunteers. The men physically restrained a 26-year-old Mexican man and forced him to hold a shirt while his picture was taken and he was videotaped...

If I were Barton I'd look closely at that last sentence, which appears to be more a statement of fact rather than just repeating what was in the AP article.

And, as far as I can determine, at post time the ACLU has not issued a correction or a different press release reflecting the information that has come to light since yesterday. There's nothing like that on the ACLU's press release page for their Immigrant Rights section or on the ACLU of Arizona's News page or on the ACLU's main press releases page. And, I couldn't find anything in google news. Perhaps they're waiting for the weekend.

(Note that the Washington Times article also includes a quote from AZ Gov. Janet Napolitano which could be read in at least two ways. In the past she's demanded that the U.S. government pay Arizona for the costs of illegal immigration, but she's also been more "liberal". She could be complaining about either the MMP or the federal government and it's not clear which.)

Previous coverage of this case is here.

UPDATE: See also "ACLU Vs. The Minuteman Project". He describes the differences between the statements of Eleanor Eisenberg of the Arizona ACLU and a couple of the ACLU's earlier press releases about the MMP.