Freezing weapons shipments to Lebanon, which the Wall Street Journal disclosed yesterday, is the right thing for the Obama administration to do. As with so many of this administration’s foreign-policy moves, however, it’s a defensive and inadequate measure, applied because it’s the only move left after better opportunities have been lost.

The time when Lebanon’s fate could have been affected through useful diplomacy was in January, when Saudi Arabia and Turkey were seeking to broker a new unity government that would have prevented the concentration of power in Hezbollah’s hands. Active U.S. support for that effort could well have convinced Hezbollah that the time was not ripe for an audacious parliamentary coup. Moreover, such support would have met with acclaim just about everywhere on earth except Tehran and Damascus.

Suspending arms deliveries to the new Lebanese government, on the other hand, is little more than a gesture. And it’s a confusing one at that.

Obama plans to maintain military ties with the Lebanese armed forces (LAF) under the Hezbollah-backed Miqati government, and will not suspend ongoing military training programs. In its practical effect, the termination of new arms deliveries amounts to accounting trivia: no one will be able to say that any U.S. arms misused by Hezbollah or the LAF were delivered after early April 2011.

It does no good to fret over the past, but at least we could learn from it. In January, we still had allies and leverage in dealing with Lebanon’s problems. Because Obama chose not to invoke those assets–chose to remain silent and disengaged as Hezbollah shattered the national-unity coalition–we are now reduced to making all-but-meaningless gestures of disapproval. It was better to have allies, common goals, and real influence. Those ingredients enabled the U.S. and other nations to give Lebanon a chance. Suspending arms shipments out of disapproval isn’t a policy alternative; it’s a sign of failure.