A good many people across the political spectrum—including some members of the Obama administration—are pressuring the president to intervene militarily in Libya. Much of the commentary has focused on establishing a no-fly zone, but there have been calls as well for enforcing a no-drive zone, or for arming or otherwise assisting regime opponents.

Those making this case appeal to a mixture of morality and realpolitik. They argue that by intervening we will prevent the slaughter of innocents and at the same time demonstrate our willingness to make good on expressions of support for freedom and security.

Secretary of Defense Robert Gates has taken the opposite position. Testifying before Congress last week, Mr. Gates pointed out that the first step in establishing a no-fly zone that would ground Libyan aircraft and helicopters would be to suppress Libyan air defenses that could threaten U.S. or allied aircraft. This would entail attacking selected targets. In other words, to establish a no-fly zone would be to go to war.

Mr. Gates was and is correct in reminding people of what implementing a no-fly zone would actually mean. But the reasons for questioning the wisdom of establishing such a zone, or taking other military action, go well beyond his warnings.

To begin with, there is no reason to believe a no-fly zone would be decisive. In fact, we have every reason to believe it would not be, given that aircraft and helicopters are not central to the regime’s military advantages. The regime could defeat the opposition without resorting to attack planes and helicopter gunships simply by exploiting its advantages in terms of foot soldiers and light arms.

What about other military steps outsiders could take? To impose a no-drive zone—which would aim to limit the government’s ability to use tanks and armored personnel carriers—would require far more extensive military force than a no-fly zone. And even if it were implemented, no number of Western aircraft on patrol could stop the movement of every military vehicle. The only way to level the battlefield would be to put trainers, advisers and special forces on the ground.

There are political reasons to question the wisdom of the U.S. becoming a protagonist in Libya’s civil war. It is one thing to acknowledge Moammar Gadhafi as a ruthless despot, which he has demonstrated himself to be. But doing so does not establish the democratic bona fides of those who oppose him. And even if some of those opposing him are genuine democrats, there is no reason to assume that helping to remove the regime would result in the ascendancy of such people.

To the contrary. Removing Gadhafi and those around him could easily set in motion a chain of events in which a different strongman, with the backing of a different tribe, took over. Or it could create a situation in which radical Islamists gain the upper hand. Either way, significant areas of the country would be beyond any government control, creating vacuums exploitable by al Qaeda and similar groups.

The wisdom of arming regime opponents is questionable for the same reason. Pre-9/11 Afghanistan offers something of an object lesson here, as the U.S. armed individuals and groups to defeat the regime backed by the Soviet Union. This policy worked in realizing its immediate goal, but in the years that followed it empowered individuals and groups who carried out an agenda hostile to U.S. interests. Arms transferred become arms over which control is forfeited.

There are many reasons to avoid making Libya the center of U.S. concerns in the region. Libya is far from the most important country in the Middle East—both in terms of political influence and its impact on the oil market. American policy makers would be wiser to focus on what they can do to see that Egypt’s transition proceeds smoothly, that Saudi Arabia remains stable, and that Iran does not.

Intervening militarily in Libya would be a potentially costly distraction for the U.S. military. It is already overextended in Iraq and Afghanistan. The last thing it needs is another vaguely defined intervention in a place where U.S. interests are less than vital.

To say that U.S. interests in Libya are less than vital is not to argue for doing nothing, but rather for making sure that the actions we take are commensurate with the stakes. In the case of Libya, asset freezes, arms embargoes, threatened prosecutions for war crimes, and the creation of humanitarian safe harbors inside the country or just across its borders would be appropriate.

Under this set of policies, Gadhafi could well survive the current challenge—regimes that are willing and able to attack domestic opponents often do. But, over time, such policies would weaken the regime while strengthening the opposition.

Such an approach will not be enough for some. But it does have the advantage of being consistent with the scale of U.S. interests in Libya and what can realistically be done to promote them

Mr. Haass is president of the Council on Foreign Relations.