The video shows officers repeatedly demanding to see Fussell's identification and Fussell refusing to show it, though he did identify himself verbally.
Rocah said Fussell was within his rights to say no.
"You don't have to show your ID to take a picture any more than you have to show an ID to read a newspaper or a book," the lawyer said.
Officers told Fussell during the half-hour incident that his filming violated the federal Patriot Act and that his audio recording broke a Maryland law against wiretapping a private conversation without consent.
Rocah dismissed both contentions, saying that the Patriot Act does nothing to restrict photography and courts have ruled that the Maryland wiretap statute does not shield officers performing their duties in public because they have no reasonable expectation of privacy.
"There is absolutely nothing they say about the law or the MTA's rules that is correct," Rocah said.
The video shows that at times during the incident, Fussell was not free to leave.
"You realize when a train gets here, you're not going to leave. You understand that?" one of the officers told Fussell.
Fussell missed at least one train to Penn Station before boarding another. Officers objected, but Fussell said he was neither arrested nor cited for any offense. He said that at no time during the confrontation did officers touch him.
Fussell said he missed the MARC train he wanted to take to Washington and had to take Amtrak. According to the ACLU letter, MTA officers followed Fussell to Penn Station and asked Amtrak Police to detain him. Fussell said he showed his ID to a railroad officer because he knew identification was necessary to take an Amtrak train. He was then permitted to board.
The ACLU said it is preparing legal action to force MTA police to comply with the Constitution. It gave the agency until Sept. 1 to make amends to Taremae and Fussell and to promulgate policies that protect the rights of photographers and videographers without any requirements for special permits.
John Wesley, a spokesman for the MTA, said the agency would have no immediate reply to the allegations in the ACLU letter.
Wesley said MTA policy, as spelled out in its media guide, asks members of the public to seek permission before filming.
"If you film, photograph or interview customers on MTA property or film any MTA property or stations, please make your request through the Office of Communication and Marketing," the policy reads.
"It doesn't say what the consequences are if you don't," Wesley said. Asked whether the policy would pass legal muster, he said "I'm not sure whether or not it's constitutional."
Osterreicher, the photographers' group lawyer, said the courts have ruled repeatedly that transit agencies cannot impose such requirements.
"If you are in public, you have a First Amendment right to photograph in public. Period," he said.
Fussell said he has photographed transit facilities in large cities from San Diego to Chicago to Washington and had never been treated the way he was in Baltimore.
"It was the first time I've been asked for ID and the first time I've been detained ever," he said.
Soon after the incident, he said, friends helped put him in touch with the Maryland ACLU. He said he's prepared to become a plaintiff and seek damages if the issues can't be resolved.
Even though his previous visit didn't turn out so well, Fussell said he would not hesitate to return to Baltimore.
"I'll come back and I'll have a camera in my hand," he said. "I don't care what happens."