Two men look at a broken window in an appartment in Donetsk, on February 12, 2015. (Vasily Maximov/AFP/Getty Images)

Paula J. Dobriansky, undersecretary of state for global affairs from 2001 to 2009, is a senior fellow at Harvard University’s Belfer Center for Science and International Affairs.

An enduring diplomatic solution to the Ukraine crisis has eluded negotiators. But even if the Minsk peace talks’ newly announced cease-fire were to hold, there is widespread agreement in the West that Russia has engaged in a quasi-war in Ukraine. Moscow has acted with some circumspection, employing intelligence agents and plainclothes special forces (the so-called little green men), but in the past several months, it has become much more brazen, deploying thousands of regular troops, backed up by artillery and armor. There is also consensus that Russian activities in Ukraine are destabilizing European security and have violated numerous international legal norms.

Unfortunately, a robust, punitive Western response, deterring Moscow from future misconduct, has been lacking. Even worse is that the West has proven unable to distinguish different types of Russian misconduct, much less to deal with them in a differentiated fashion.

Russia’s grave violations of international humanitarian norms, especially the law of armed conflict, should be a main target of Western criticism, drawing a decisive response. That response should come not only in the form of diplomatic and economic sanctions but also include investigations and prosecutions at the International Criminal Court at The Hague.

Moscow’s annexation of Crimea and its invasion of eastern Ukraine constitutes aggression in violation of the U.N. Charter, numerous European treaties and other international undertakings, but the ICC currently lacks jurisdiction to prosecute crimes of aggression. It does have ample authority to investigate crimes against humanity and certain types of war crimes, namely grave violations of the 1949 Geneva Conventions.

There is no doubt that numerous war crimes have been committed by Russian troops and Russia-controlled Ukrainian separatists. The most prominent examples include the July 17 downing of Malaysia Airlines Flight 17 and the Jan. 24 missile attack on the market in Mariupol. Both involved non-military targets, and hundreds of civilians perished. These actions constitute at best a reckless disregard of civilians during the conduct of military operations and at worst deliberate attacks on civilians. Under either interpretation, Russian President Vladi­mir Putin, who commands the armed forces, and the entire military chain of command have committed grave violations of the Geneva Conventions.

Significantly, unlike some other investigations the ICC has undertaken, the legal basis for ICC jurisdiction over Ukrainian territory is well established. Ukraine signed the Rome Statute — the treaty that established the court — and sought to ratify it, only to be told by the country’s Constitutional Court that the treaty was inconsistent with the Ukrainian constitution. (Russia has also signed the Rome Statute but has yet to ratify it.)

Even though Ukraine is not an ICC member, it has granted the ICC jurisdiction to investigate allegations of crimes against humanity that it believes were committed during the tenure of former president Viktor Yanukovych, focusing particularly on the period from Nov. 21, 2013, to Feb. 22, 2014. Russia’s annexation of Crimea and its invasion of Eastern Ukraine took place after that, but nothing prevents the Ukrainian government from broadening the scope of its original ICC referral to include Russian military operations in Ukraine. Such a referral would be given additional legal and symbolic weight if it were supported by the existing ICC state parties, a scenario clearly provided for under court rules.

Of late, the ICC has sought to broaden the scope of its investigations and prosecutions. Toward that end, it has accepted the Palestinian bid to become a member of the court, despite the fact that Palestine does not satisfy most of the traditional attributes of state sovereignty. Even before that, the ICC indicated that it had jurisdiction to investigate Israel’s military operations in Gaza. These decisions are both legally questionable and enmesh the court into hotly contested Middle Eastern issues. Neither decision has helped the ICC’s still-uncertain reputation for legal probity and absence of political bias.

Hence, the court’s failure to take action against Moscow’s war crimes casts doubt on its integrity. This is particularly poignant because the ICC was created to ensure that war criminals would not be accorded immunity and that purely legal imperatives, rather than politics, would drive prosecutorial actions. As such, the ICC’s inaction should be of grave concern to European states and nongovernmental humanitarian organizations, particularly the International Committee of the Red Cross, which have been the primary movers in the Rome Statute negotiations.

Failure to call Russia to account will only embolden Moscow to continue on its course of action. Pragmatic and legal imperatives call for a course correction. This is a rare circumstance in international affairs, and it’s one not to be forfeited. As European leaders continue to consider how to deal with Russia’s aggression, the ICC investigation of Russian war crimes should be at the top of the agenda.