Hardly a week seems to go by without North Korean leader Kim Jong Il deciding to once again chest-thump President Obama in an increasingly dangerous game of school-yard bullying. US planes and spy satellites are now monitoring the movements of a ship that looks to be the latest provocation.

In just the last month, we've seen Pyongyang conduct a nuclear test, threaten war, sentence two US journalists to prison camp and promise another long-range missile test, this time toward Hawaii.

But the latest nose-tweak, according to press accounts, centers on a North Korean cargo ship now at sea with a suspected load of contraband in defiance of a week-old UN resolution, which, among other matters, prohibits Pyongyang's arms exports.

Kang Nam, the North Korean-flagged ship, could be carrying components or materials for ballistic missiles, nuclear or chemical weapons -- even conventional arms. Some assert it's been involved in proliferation activity before.

Of course, Kim's regime has already transferred ballistic missiles to Pakistan, Iran and Libya and was infamously building a nuclear reactor in Syria before Israel destroyed it in 2007. This cargo isn't likely helpful to international security (or US interests), either.

Kang Nam's final destination is unknown, but it's reportedly heading south in the Yellow Sea, likely hugging the Chinese coast to stay out of international waters and evade detection.

Unfortunately, the new UN resolution offers only limited help. Passed last week, it is an improvement on the UN's response to North Korea's April missile test: Back then, the United Nations basically sent Kim a mean letter; now, it's imposing some new, targeted sanctions.

Better yet, it also encourages nations to cooperate with a successful Bush-era policy -- the Proliferation Security Initiative, which promotes the use of national laws to seize WMD/missile cargoes that happen into the territory, waters or airspace of its 90-plus partner countries.

For instance, if Kang Nam makes a port call in Singapore en route to its final destination for fuel or supplies, local authorities are within their right to search the ship for troubling cargo -- and seize it if necessary.

Beyond that, the resolution doesn't have a lot of teeth. But other responses are possible. A US warship could intercept the Korean ship and request permission from its skipper to board. Of course, an OK is unlikely unless the captain and crew never plan to return to North Korea -- and don't have any concerns about the families they left behind in the regime's hands.

A forced boarding of the ship on the high seas to inspect or seize it is another possibility, but it could be seen as an act of war. (And Pyongyang has vowed to see it that way.)

Indeed, the chairman of the Joint Chiefs of Staff, Adm. Mike Mullen, told reporters the UN resolution "does not include an option for opposed-boarding or noncompliant boarding" and that the United States would play along.

With the spotlight on it, Kang Nam might duck into a Chinese port, since Beijing is always reluctant to come down too hard on Pyongyang and was hesitant on even this watered-down resolution. Spooked, the ship might even return home with its illicit load. But we probably won't get such an easy resolution to this brewing crisis.

If the Obama administration believes that Kang Nam is carrying a prohibited cargo in its hold, whose delivery runs counter to US interests, it must take steps to prevent it from reaching its destination.

To date, Obama's North Korea policy has been amorphous and flabby at best. Another anemic response to Pyongyang's troublemaking simply invites more belligerence -- already at levels unprecedented in at least 10 years. Competently stopping this shipment would be a good, first step in knocking Kim off his game.

Peter Brookes is senior fellow for National Security Affairs in the Davis Institute at The Heritage Foundation.