The questions seem deceptively simple? Who is "a journalist"? What, for that matter, is "journalism"? And who should we welcome as a newspaper proprietor? Discuss: or rather wander into a moral maze that, this summer, grips editors and politicians alike.

Here's the judiciary committee of the US Senate trying to frame a "shield law" that will give reporters some protection when government and its agencies seek to bug, arrest or demand to know sources. Its embryo bill says that a journalist is someone "who has a primary interest to investigate events and procure material", informing the public through interviews and observation. He or she sets out to report the news; he or she must intend to publish that news.

But, asks one senator, is that protection for WikiLeakers? Surely we only want to help "real reporters", who draw salaries for their work, says another. The congressional equivalent of our own dear Westminster lobby system insists that the correspondents it grants passes to are full-time on some corporate payroll. And the senator driving the bill, Charles Schumer, doesn't exactly help. "The world has changed," he insists. "There are people who write and do real journalism in different ways than we're used to – and they should not be excluded."

So there you have it – or rather don't, because the committee can't agree and has gone on holiday instead. We want to protect "real" journalists, but the precise nature of that reality eludes us. And meanwhile reality itself assumes another dimension as Glenn Greenwald and Edward Snowden keep up their flow of exclusives about security surveillance. Is Greenwald, a Guardian columnist of vivid, libertarian views, a "real" journalist? Not according to some Obama administration voices and rather too many sonorous broadcasters and upmarket commentators. Greenwald, they say, is "an activist" – which means he isn't fair, balanced and suitable for employment by "respected" organisations. Therefore his work is somehow tainted, so not worth overmuch reaction, sitting somewhere beyond the pale.

Enter Jack Shafer, one truly respected media columnist for Reuters: "I'd rather judge a work of journalism directly than run the author's mental drippings through a gas chromatograph to detect whether his molecules hang left, right or cling to the centre."

From the early pamphleteers – Tom Paine for one – to the muckrakers who fought injustice such as Nellie Bly; from Rachel Carson's Silent Spring to Ralph Nader's Unsafe At Any Speed; from Mother Jones to the Pentagon papers, the words that shook America mostly came from passionate reporters with a cause to champion.

The point can equally be made about British journalists – from John Wilkes to Alfred Harmsworth – and it draws a line in the sand. Woodward, Bernstein and Co don't sit on one beach while HL Mencken sits on another. Journalism in action is defined not by boxes ticked or examinations passed, but by the stories produced. What matters in the end is what comes out, what affects the public consciousness – not the rulebooks that govern its practices.

We dub the brave men and women of Homs who venture onto blazing streets with their mobile phone cameras "citizen journalists" for good reasons. They are photographing something the world needs to see. When they die, as they often do, their death is a blow to journalism – and our attempts to put them in some lower category of loss is an affront (one that human-rights warriors do not share).

Of course lordly TV presenters in plush studios don't like to be associated with the likes of Greenwald. Why, he believes too much in what he reports. He's involved. Of course university journalism professors are keen on ethical codes and standards of conduct, because if these matters are pushed into a secondary place they diminish the importance of the education that pays their wages. And of course judges, and the politicians who appoint them, like to construct structures of behaviour they deem to deserve their public's trust.

Some of the time that's all very well (if you like lugubrious Leveson debates, that is). Some of the time it's a necessary framework. But time and again it's what comes out that counts, not how it emerges through a web of existing perceptions. Greenwald is a journalist. Edward Snowden, releasing individual stories for individual purpose, exemplifies the impulses of journalism. And nobody, in whatever judiciary committee hearing, should imagine that a law can truly shield them. That's not what journalists are about.

And as for their proprietors …