While the ceasefire agreement between the Ukrainian government and separatist rebels in the eastern part of the country seems largely to be holding, a recent showdown in Kiev between a Ukrainian oligarch and the government revealed one of the country’s ongoing challenges: private military battalions that do not always operate under the central government’s control.

In March, members of the private army backed by tycoon Ihor Kolomoisky showed up at the headquarters of the state-owned oil company, UkrTransNafta. The standoff occurred after Kiev fired the company’s chief executive officer — an ally of Kolomoisky’s. Kolomoisky said that he was trying to protect the company from an illegal takeover.

More than 30 of these private battalions, comprised mostly of volunteer soldiers, exist throughout Ukraine. Although all have been brought under the authority of the military or the National Guard, the post-Maidan government is still struggling to control them.

Ukraine’s military is so weak that after the Russian Federation seized Crimea, Russian-sponsored separatists were able to take over large swathes of eastern Ukraine. Private battalions, funded partially by Ukrainian oligarchs, stepped into this vacuum and played a key role in stopping the separatists’ advance.

By supplying weapons to the battalions and in some cases paying recruits, Ukraine’s richest men are defending their country — and also protecting their own economic interests. Many of the oligarchs amassed great wealth by using their political connections to purchase government assets at knockdown prices, siphon off profits from state-owned companies and bribe Ukrainian officials to win state contracts.

When the Maidan protesters overthrew former President Viktor Yanukovich, they demanded that the new government clamp down on the oligarchs’ abuse of power. Instead, many became even more powerful: Kiev handed Kolomoisky and mining tycoon Serhiy Taruta governor posts in important eastern regions of Ukraine, for example.

Many of these paramilitary groups are accused of abusing the citizens they are charged with protecting. Amnesty International has reported that the Aidar battalion — also partially funded by Kolomoisky — committed war crimes, including illegal abductions, unlawful detention, robbery, extortion and even possible executions.

Other pro-Kiev private battalions have starved civilians as a form of warfare, preventing aid convoys from reaching separatist-controlled areas of eastern Ukraine, according to the Amnesty report.

Some of Ukraine’s private battalions have blackened the country’s international reputation with their extremist views. The Azov battalion, partially funded by Taruta and Kolomoisky, uses the Nazi Wolfsangel symbol as its logo, and many of its members openly espouse neo-Nazi, anti-Semitic views. The battalion members have spoken about “bringing the war to Kiev,” and said that Ukraine needs “a strong dictator to come to power who could shed plenty of blood but unite the nation in the process.”

Ukraine’s President Petro Poroshenko has made clear his intention to rein in Ukraine’s volunteer warriors. Days after Kolomoisky’s soldiers appeared at UkrTransNafta, he said that he would not tolerate oligarchs with “pocket armies” and then fired Kolomoisky from his perch as the governor of Dnipropetrovsk.

By bringing the private volunteers under Kiev’s full control, Ukraine will benefit in a number of ways. The volunteer battalions will receive the same training as the military, which should help them to better integrate their tactics. They’ll qualify for regular military benefits and pensions. Finally, they will be subject to military law, which allows the government to better deal with any criminal or human rights violations that they commit.

Poroshenko must contend with challenges like widespread corruption, economic collapse and the Russian-supported separatists. With rumors of a possible spring offensive planned by the separatists, he will not want to risk more confrontations like the one involving Kolomoisky. The Ukrainian government is not going to be able to govern their country if powerful private militias operate as freelancers outside of state control.

Poroshenko’s effort to rein in Ukraine’s volunteer warriors — like his fight against corruption — may be a case of two steps forward, and one step back.