There's nothing remarkable about Russian President Vladimir Putin's visit to Mongolia on Tuesday — he's due to meet the country's leader, hold talks on developing bilateral ties and attend a gala reception.

What is unusual is that Mongolia, as a member of the International Criminal Court, should have arrested the Russian president as soon as he landed on Mongolian soil Monday evening.

Putin is the subject of an international arrest warrant issued by the ICC in March 2023. The court alleged that he is responsible for war crimes, with a particular focus on the unlawful deportation of children from Ukraine to Russia.

At the time, the Kremlin described the ICC's actions as "outrageous and unacceptable" and said they had no effect on Russia, which is not a member of the ICC.

Mongolia has now found itself in hot water as Putin visits the country — his first visit to an ICC member state since the arrest warrant was issued — with apparent impunity.

Under the Rome Statute, the founding treaty of the ICC that came into effect in 2002, ICC member states are obliged to detain and surrender to the court any persons who are subject to an ICC arrest warrant, if they set foot on their soil.

The court has no way to enforce the rule, however, and Mongolia defied it by welcoming Putin with a guard of honor as he met President Ukhnaagiin Khurelsukh in the capital, Ulaanbaatar, on Tuesday.

Mongolia's risky move has caused consternation at the ICC, which is based in the Netherlands, and in Ukraine, which was invaded by Russia in February 2022.

A spokesperson for the ICC, Fadi el-Abdallah, told the BBC last Friday that Mongolia had an "obligation" to comply with the arrest warrant and said "in case of non-cooperation, ICC judges may make a finding to that effect and inform the Assembly of States Parties of it. It is then for the Assembly to take any measure it deems appropriate."

He did not specify what measures could be taken, however, and clarified that the ICC does allow for some exemptions to the rule, such as when a country could be forced to "breach a treaty obligation" with another state or where it would violate "diplomatic immunity of a person or property of a third state," the BBC report noted.

International legal experts warned Monday that Mongolia's failure to fulfil its obligations to the ICC will very likely have some consequences, with some mooting the possibility of prosecution.

"ICC States Parties should not be inviting persons subject to an ICC arrest warrant to visit their countries for any reason. Full stop," noted Mark Ellis, executive director of the International Bar Association, or IBA, an organization representing the global legal profession.

"Mongolia's membership in the ICC and its respect for the rule of law demands that it comply with this arrest warrant or let President Putin know that he is not welcome in Mongolia. This is a moment when Mongolia, as a State Party, has to put law over politics," he said in emailed comments Monday.

The IBA went on to warn that Mongolia, a member of the ICC since 2002, could face "consequences in the event of non-cooperation." Though it did not specify what these could be, there is speculation that Mongolia could now be prosecuted by the ICC.

Mongolia has not commented or responded to the criticism over Putin's trip. CNBC has contacted the country's Foreign Ministry for comment.

Russia was sanguine about the trip to Ulaanbaatar beforehand, with no apparent worries over a potential arrest scenario in a country where Moscow aims to extend its regional influence and energy infrastructure.

Kremlin spokesman Dmitry Peskov told reporters last Friday that the Kremlin had "no worries" about the trip, stating that Russia's leadership has "a wonderful dialogue with our friends from Mongolia."

Russian media agency Tass cited Russian presidential aide Yury Ushakov as stating that the two leaders will discuss cooperation between Moscow and Ulaanbaatar "in industrial production, agriculture and railway transport" as well as educational programs and exchanges.

Democracy Fellow with the Center for European Policy Analysis, Elena Davlikanova, commented that Russia was using the trip to "mock the ICC," with the economically supplicant country a deliberate choice for a visit to test the ICC's mettle.

"Of course, Putin would never have traveled if there was any chance of an arrest. The country had already assured Moscow the president would not be detained," she noted in analysis Monday.

"Sandwiched between two powerful neighbors, Russia and China, Mongolia has long been constrained in its freedom of maneuver, so Putin's choice makes ruthless sense," she added.

For Russia, the trip offered not only a distraction from Ukraine's incursion into the Kursk border region but also a way to "help maintain Putin's image as a strong leader at home and abroad," she said, adding that the trip also helped to undermine the ICC and any prospect of future prosecution of suspected war crimes.

"Putin is willing to defy international legal norms to undermine international law. Hungary and Armenia, also ICC members, have assured the president that he would not be arrested on their soil, further eroding the court's effectiveness. If the world order continues to weaken, the prospects for a tribunal for Russian war criminals, reparations and accountability would diminish significantly, dashing Ukraine's hopes of a just peace," Davlikanova said.

Ukraine's Foreign Ministry spokesman, Heorhiy Tykhyi, said Monday on Telegram that "Mongolia has allowed an accused criminal to evade justice, thereby sharing responsibility for the war crimes." He added that Kyiv would work with its partners "to ensure that this has consequences for Ulaanbaatar."

The European Commission on Monday called on Mongolia to meet its obligations to the ICC.

"Mongolia, like all other countries, has the right to develop its international ties according to its own interests, however ... Mongolia is a state party to the Rome Statute of the ICC since 2002 with the legal obligations that it entails. We have raised our concern about the visit and stated our position of the ICC clearly via our delegation in Mongolia," commission spokeswoman Nabila Massrali said Monday.

Human rights campaigners have also criticized the move with Human Rights Watch and Amnesty International among the groups calling for Mongolia to arrest Putin.

Altantuya Batdorj, executive director of Amnesty International Mongolia, commented Monday that "Mongolia's international legal obligations are clear."

"President Putin is a fugitive from justice. Any trip to an ICC member state that does not end in arrest will encourage President Putin's current course of action and must be seen as part of a strategic effort to undermine the ICC's work to prosecute suspected war criminals," Batdorj said, in comments posted online.