With the beginning of hurricane season only 40 days off, Haitians should be worried about protection from the annual onslaught of stormy weather, but instead another crisis is shaking the Caribbean’s perennially troubled country: A rogue force of “paramilitaries” that neither the government of President Michel Martelly nor anyone else is eager to confront has become a dangerous menace to public order, raising questions about who’s in charge.

For several weeks, the presence of this unofficial army has been hard to miss. In February, they occupied abandoned army barracks, settling in without much objection from any authority. Gradually, they have become bolder and bolder. They paraded around Cap-Haitien and Port-au-Prince earlier this month on Haiti’s traditional Constitution Day, and last week as many as 50 members, some of them armed, disrupted Parliament, forcing lawmakers to suspend business for the day.

The force is said to number anywhere from 2,000 to 3,500 mostly young men and women, apparently led by ex-army officers. Officially, Haiti has had no army since it was disbanded years ago by former President Jean-Bertrand Aristide at U.S. insistence because it was a persistent threat to civilian control. But many of those officers never resigned themselves to being out of power.

Early on, the force was seen primarily as a nuisance, a distraction from the business of getting Haiti back on its feet after the disastrous 2010 earthquake. But the intrusion of the paramilitaries in Parliament should end all hope that they will just fade away.

Although the force is said to be only “lightly armed,” it poses a threat to the government because no one knows who’s behind them or what their intentions are. Haitians and members of the international community working to rebuild the country are asking whether they represent a force unto themselves more powerful than Mr. Martelly’s government.

All of this comes at a time when there is no effective government in place. Former Prime Minister Garry Conille, who had the support of the international community, resigned on Feb. 24 under pressure from Mr. Martelly. He remains in office until a successor is ratified by Parliament, but without effective authority. At the same time, 10 members of the Senate will see their terms expire in May, but no date has been set for a new election because of the endemic political bickering that makes Haiti a nearly ungovernable state.

The U.N. security force in Haiti issued a statement after the caper in Parliament deploring it as “an unacceptable act of intimidation” and put its own military patrols in place to prevent a repetition. But it failed to pursue the outlaw force and has refused to take responsibility for putting an end to the threat it represents.

Similarly, Mr. Martelly — from a hospital in Miami where he was said to be recovering from a pulmonary ailment — issued a statement declaring that “the formation of a new public force can only be done in an orderly and disciplined fashion and in observance of the laws in force.”

That sends a mixed signal. Mr. Martelly must clearly and unequivocally label them outlaws and ask for help from the U.N. force and from the United States, which has also failed to speak up in defense of Haiti’s stability.

The paramilitaries have to be disarmed and disbanded, and their leaders arrested for posing a threat to public order. Haiti has enough problems getting the country back together without having to deal with a rogue army in its midst.