In their defense, what else can they say? If they say nothing, they’ll be pilloried for silence in the face of aggression. If they get too explicit about the consequences of line-crossing, everyone will think of Obama’s humiliation over his Syria “red line” and laugh. There’s nothing the U.S. can do to stop Russia from knocking heads and reclaiming Crimea if it wants to. Which means all that’s left is the traditional stern yet scrupulously vague admonishment.

Kerry, in comments that highlighted Washington’s rising suspicion of Moscow, said the U.S. is watching to see if Russian activity in Crimea “might be crossing a line in any way.” He added that the administration would be “very careful” in making judgments about that.

“While we were told that they are not engaging in any violation of the sovereignty and do not intend to, I nevertheless made it clear that could be misinterpreted at this moment,” Kerry said. “There are enough tensions that it is important for everybody to be extremely careful not to inflame the situation and not send the wrong messages.”

Meanwhile:

Carney says US watching closely to see if Russia crosses "intervention line" in Ukraine.

— Mark Knoller (@markknoller) February 28, 2014

What on earth is an “intervention line” and how has Russia not already crossed it? AP photographers snapped pics this morning of Russian personnel carriers on the move inside Crimea:

BREAKING: AP in #Crimea spots convoy of Russian armored personnel carriers en route to capital http://t.co/BZhOPl2RHe pic.twitter.com/mjPeVQfCb9

— Haaretz.com (@haaretzcom) February 28, 2014

Between that and the seizure of the airports in Sevastopol and Simferopol, for which, apparently, Russia is now admitting responsibility, Ukraine’s new interior minister says this has become a “military invasion and occupation.” Seems like the fabled “intervention line” has been crossed. Then again, if there’s any one lesson to take from the Syria “red line” debacle, it’s that the White House is willing to look the other way repeatedly at violations in order to avoid having to enforce its lines. Remember, Assad’s side was accused more than once of chemical attacks before the big one last August that finally compelled the White House to act. Could be that Obama and Kerry are following a similar approach here: So long as the movements of Russian troops can kinda sorta be explained as defense of their naval bases in Crimea, that’s technically not an “intervention.” Just like, er, this isn’t an intervention either:

Crimean airport: All incoming and outgoing flights cancelled tonight. Airspace closed. #Simferopol #Crimea #Ukraine pic.twitter.com/pqVbpE1W9x

— Lawendler (@ArtWendeley) February 28, 2014

https://twitter.com/joshuafoust/status/439472812693413888

The White House’s plan, I assume, is to hope that Putin will be satisfied with this little bit of muscle-flexing and agree to talks on the disposition of the country rather than take parts of it by force. The goal is probably partition: If the choice is between letting eastern Ukraine and Crimea leave and a major war that Russia will have much more interest in prosecuting than the EU will, why not try to secure Russian acquiescence in letting western Ukraine go and call it a day? The Russians aren’t waiting around on their end of this:

There was a draft law debated to this effect in the Russian State Duma. Now, this announcement on the Russian Foreign Ministry’s Facebook page:

“Consulate General of the Russian Federation in Simferopol urgently requested to take all necessary steps to start issuing Russian passports to members of the “Berkut” fighting force.”

In other words, Russia is now urging the nationalization of Yanukovych’s riot police.

Why is this important? Before Russia invaded Georgia in 2008 they issued passports to ethnic Russians.

At now, the Russian State Duma is discussing a draft law for adding a new subject of the Russian Federation, i.e. Crimea. In other words, Russia is taking many steps that it took before invading Georgia. This looks to be an attempt to annex Crimea.

I’m … reasonably sure that full annexation would cross the “intervention line,” requiring some sort of U.S. response, but we’ve been through too much to underestimate O’s ability to retreat from his own ultimatums. Stay tuned.

Update: The fact that Kerry’s saying things like this makes me think Russia’s not too worried about crossing anyone’s line.