When President Obama wrapped up his remarks on the Boston Marathon, reporters--in the room and on Twitter--quickly checked the language. No, the president had not referred to "terrorism." What does that mean?
It means a number of things, and it depends on who's saying it. If/when a subject (or subjects) gets charged for the bombings, yeah, it matters whether they're prosecuted for "terrorism" or not, and whether anyone else is prosecuted for conspiracy to commit terrorism. But we're not there yet--the discussion is whether politicians mean anything when they say "terrorism" happened in Boston. Right now, they don't. No international terrorist organization has even taken credit. Like Bruce Schneier says, there's no good reason for people to panic about the T-word. Look at four possible outcomes if the act was, indeed, terrorism.
Islamic terrorism. If that's what happened, it's the first successful attack in the United States since the 2009 killings at Fort Hood; if that's too controversial, it's the first successful attack here since 2001. The people with the most to say and gain, politically, are the people who accused the Obama administration (and even the Bush administration) of being too PC to draw links between extremist branches of Islam and terror, or even too PC to racially profile. Likely legislation? Well, in Britain, fear of Islamic terrorism led to a debade about criminalizing "terror glorification," something that would be tough to do here within in bounds of the First Amendment (and good for us). The response would depend entirely on the investigation--the ranks of "unindicted co-conspirators" tend to mushroom after these situations.
Right-wing terrorism. The I-told-you so crowd is entirely different: It consists of people who tried to say, in 2009, that DHS should fret about "patriot" movements and people with military training returning from war to make war on the government. Likely legislation? More like a free hand for the president to criticize "anti-government" extremism. In a situation like this, the Infowars-esque conspiracy theorists do major damage to their own side, making government critics look ever less reasonable.
Left-wing terrorism. Same as above, but the culprits can be identified as believers in some left-wing cause--most of this, recently, has been some kind of eco-terrorism. Likely legislation? See above, but replace "the president" with "Republicans."
Unclassifiable kook terrorism. In this case we merely get the legislative push common to every scenario--greater pressure for homeland security funding, and for more surveillance in cities.
Read more on Slate about the Boston Marathon bombing.