The Serbian soldier blocking the bridge cradled his AK-47 assault rifle as he delivered a ruling that brooked no argument: You cannot cross the river. Not today.

We implored him to reconsider. We are journalists. We've driven all the way from Belgrade. Here are our credentials.

No. This road is closed.

Zashto? (Why?)

Ne! (No.)

We never made it to Zvornik, the Bosnian town just across the river. When it came to press access, the final word belonged to the men with guns. As we later learned, the Serbs had plenty to hide that spring day about their activities in eastern Bosnia.

I was reminded of that instant -- admittedly a very different set of circumstances -- when we received a call last week at ProPublica from Lance Rosenfield, a freelance photographer we had hired to work in Texas City, Texas, on stories about BP's refinery there.

Rosenfield said he had been detained by local police after snapping a picture on the road into Texas City. Rosenfield said he had shown the officers and a BP security guard a letter from ProPublica that said he was on assignment. Police said he would be "taken in" if he did not let them look at the photos in his camera.

The senior officer present, Cpl. Thomas Robison, pressed Rosenfield to describe ProPublica's forthcoming story.

Rosenfield demurred but did allow police to review his photos. No threat to national security was detected -- the pictures were innocuous shots of the refinery and signage nearby. Rosenfield was eventually allowed to leave after being warned to clear further photography with the local authorities. At the request of police, he turned over his social security number and date of birth which were promptly given to the BP security officer who was present.

The men with guns had made their determination. It doesn't appear that they had much of a legal or logical basis to do so.

Why would potential terrorists take photos from a public street when they can view detailed reasonably high-resolution satellite photos via Google? What could possibly be gained from a ground-level shot, even with a telephoto lens?

Michael Marr, a BP spokesman in Texas City, said that the company acted because "an unidentified man" had been seen taking photos near refinery facilities, including "marine loading operations." Marr said Department of Homeland Security and U.S. Coast Guard regulations require the company to report anyone "appearing to be engaged in surveillance of any kind (picture taking, note taking, shooting video, asking strange questions, etc)."

David Schulz, a media lawyer who teaches at the Columbia Law School, told me that the rules are not so broad as to allow inspection of a journalist's unpublished photos. "It is not against the law to take photos from a public street," he said.

"While federal regulations do require critical facilities to report suspicious activities, they do not sanction police demands to inspect photos taken by a working journalist," Schulz said. "A demand to see the photos smacks of censorship -- monitoring the news before it's published, with police acting as censors of what they like and don't like. Police simply don't have the power to do that, and we should all be concerned when provisions intended to safeguard our security are twisted to intimidate journalists."

In the weeks since the Deepwater Horizon exploded in the Gulf of Mexico, local authorities in Louisiana and elsewhere have made it more difficult for reporters and television crews to follow the story, restricting access to public beaches and waterways. More recently, the Coast Guard has set limits on how close news crews can come to booms and oily beaches.

There is, of course, good reason to keep the press away from potentially dangerous pollution sites. And there's at least an equally valid public policy rationale for keeping an eye on people who are photographing critical infrastructure like a refinery.

But the public and the press have good reason to be suspicious when a major corporation and the government try to curtail photography or reporters' firsthand access. The American Civil Liberties Union of Louisiana has raised questions about why reporters' movements have been restricted by local sheriffs.

And it's even harder to understand what circumstances justify allowing the police to review a journalist's work before publication.

News organizations fight hard to preserve the privacy of unpublished notes and photographs. The reasons are understandable. People often talk to reporters in confidence. We are not an arm of law enforcement and wouldn't want potential sources to feel that every dealing they have with us is open to scrutiny. News organizations routinely fight to quash subpoenas for unpublished material.

In the Texas City case, there was no confusion about Rosenfield's status as a journalist. He was carrying a letter from ProPublica confirming his assignment. The police officers who detained him made no effort to call editors here before questioning his credentials and detaining him. Marr's statement suggests that he was taking pictures near a marine loading facility. That may be true, but then a good swath of the Texas City is "near" one part of the port or another. And none of the photographs depict such facilities themselves.

This wasn't the first time journalists and the Texas City police have been in conflict. Capt. Ross Clements told me the police have a "standard practice" of reviewing photos snapped by tourists and news photographers because shots of "critical infrastructure" could be of use to terrorists.

A photographer for a local newspaper, The Galveston County Daily News, was detained in 2008 after shooting pictures of refinery workers trying to contain a leak at Marathon Oil Co.

Cpl. Robison, the local police's contact with the Joint Terrorism Task Force and the same officer who tried to get Rosenfield to disclose the contents of ProPublica's story, defended the policy, telling the Daily News:

"There's no law that says you can't take pictures from a public roadway, but the issue becomes: Are any of the shots compromising security measures?"

Michael Smith, associate editor of the Daily News, said the paper has pressed repeatedly for police to identify a federal law that permits them to review photos.

"As far as I can tell, there is no law that grants the police this power," he said.

"Nobody can point to a law of the United States of America or the State of Texas that allows police to do this," Smith continued. "This is an assumed power that the police have taken on themselves based on this amorphous notion that the demands of the security state allow this and if you're a good citizen, you shouldn't make a fuss."

To be fair, the streets of Texas City are nothing like the back roads of war-torn former Yugoslavia. But it's worth recording this historical note: The day I was stopped from entering Zvornik, a group of paramilitary soldiers had begun an "ethnic cleansing" that would leave hundreds of Muslim civilians dead. It was among the more brutal massacres of the war. One reason we know what happened is that one of the paramilitary groups invited an American photographer to accompany it.

If you don't think access matters, take a look at his photos.