Of the approximately 40 national legislatures I've had the opportunity to visit, few have been as open to the public, as easy to walk into off the street and observe up close, as Ottawa's. Many have started out that way – but it is hard to find a country whose national seat of government has not been threatened with, or actually experienced, the sort of violence that Ottawa did on Wednesday. The angry gunman in the legislature is a constant, distressing phenomenon worldwide, and the way we respond tends to be depressingly similar: by turning democracy into a fortress.

Some places only changed recently. In the mid-2000s, I went to Copenhagen to interview some cabinet ministers. I stepped right off the street into the handsome legislature building, was waved through a perfunctory security desk and into a small sitting room. There, through an open door, I saw Prime Minister Anders Fogh Rasmussen working at his desk, where he could virtually look out to the street.

In the next few years, a series of terrorist threats against Denmark's legislature came to light, and that legislature sprouted the all-too-familiar encrustation of fences, bollards, X-ray facilities, heavily armed details and closed doors. There is, in most capitals, a palpable sense of loss.

Story continues below advertisement

All terrorist attacks are, by definition, symbolic. The assailants are not seeking to overcome their perceived enemy by military defeat or to use persuasion to change the state of affairs they detest, but rather to create a sense, among public and officials, that their most open, welcoming and observed institutions – markets, border crossings, vacation resorts, public-transit systems, hotels, airports, trade centres, and legislatures – will never again, so long as that state of affairs continues, be places where people can peacefully gather without fear of physical harm.

As such, attacks on legislatures and parliaments are among the most primal, well-established and frequent forms of terrorist attack, reaching back to the origins of terrorism and taking place, in one country or another, almost every year.

This year alone, we have seen terrorist attacks on Somalia's parliament (in which 10 were killed), a series of terror attacks on Ukrainian parliamentarians, and a spectacular and apparently well-developed plot to attack Australia's parliament thwarted shortly before its execution. And this has not been an exceptional year.

There is a tragic sameness to these attacks: Similar zealous individuals, seeking oddly similar outcomes, achieving similar, self-defeating end results. They leave the public feeling violated. They discredit whatever cause the terrorists were nominally fighting for, and end any dialogue on the matter. They damage whatever sense existed that these buildings were the people's house, open to all. They tend to produce, in response, permanent security measures whose character is contradictory to the daily practice of democracy.

The grim phalanx of security barriers, walls and heavily armed guards that surround Washington's Capitol and White House do not have their origins in the Sept. 11 attacks (in which one of the jetliners was meant to have struck the Capitol), but rather in an event that took place 60 years ago, and established the template for legislative terror.

On March 1, 1954, a woman and three men entered the visitors' gallery of the House of Representatives, pulled out semi-automatic pistols, and began firing at the lawmakers below. They wounded five congressmen, one of them seriously, before being arrested. As they fired, they unfurled a Puerto Rican flag and shouted "Viva Puerto Rico!" As radical nationalists who saw the United States as an occupying force – and embodying the nationalist terrorism that dominated that period – their mood and motives bore no small resemblance to this century's attacks.

Threats to Washington's seat of power continued to mount over the coming decades: First, plots against Washington by the far-left militias whose bomb attacks terrified the United States in the 1970s and culminated in the 1983 bombing of the Senate by a far-left group; then threats by right-wing anti-government groups in the 1990s (including a 1998 attack in which a gunman shot his way into Congress, killing two policemen, and entered a congressman's office before being shot himself) then this past decade's twin threats by both Islamist and right-wing zealots, including the recent string of fence-jumpers. Each set of threats has rendered Capitol Hill less friendly to its citizens.

Story continues below advertisement

In London, we are accustomed to viewing Westminster from behind a virtual moat of iron and concrete and Downing Street from behind thick iron bars and lines of rifle-toting guards shutting off the entire block. Whenever I've visited No. 10 or No. 11 (the Chancellor of the Exchequer's residence), I've undergone extensive security checks, interviews and searches before being allowed to approach the big black doors. This wasn't the case a few decades ago: You could simply stroll up.

What changed that was a series of terror attacks on democratic institutions: Following the lethal Irish Republican Army bomb attack on prime minister Margaret Thatcher and her cabinet in Brighton in 1984, a series of armed attacks on Parliament were intercepted, and millions of pounds were spent adding defences to Britain's seat of government. Then, in 1991, the Irish Republican Army launched a mortar attack on 10 Downing St.; one of the powerful weapons exploded only metres from prime minister John Major's cabinet meeting. The result was even more impenetrable security, which intensified in the years of the Iraq war and made the mother of all parliaments far less visible to its people.

In all these decades of attacks, very few politicians have been killed. Guards and policemen, as in Ottawa, are the most common victims. But there has been a larger cost, in the sense of community that ought to surround legislatures: It's just not the same when you have to scale a fortress to get inside.