Socialist Sen. Bernie Sanders (I-VT) told moderators at Tuesday’s Democrat Party debate that Turkey’s alliance with the United States no longer exists in the event that the government there commits “mass slaughter.”

Sanders was referring to Turkey’s “Operation Peace Spring,” an invasion of Syrian Kurdistan (Rojava) whose stated mission is to eradicate the Kurdish presence in Kurdistan and replace the locals with mostly Arab Syrian refugees. The Syrian Democratic Forces (SDF), a U.S.-allied militia operating in Rojava, has warned that the plan necessarily requires ethnic cleansing.

“Turkey is not a U.S. ally when they invade another country and engage in mass slaughter,” Sanders asserted.

Turkey is a member of the North Atlantic Treaty Organization (NATO), a post-World War II alliance whose treaty provisions do not state that a member is automatically expelled from the group if they “engage in mass slaughter.” The treaty binds Washington to recognize an attack on Turkey as an attack on the U.S. homeland and act accordingly.

Turkey joined NATO in 1952 and, while not fulfilling the stated goal of all NATO countries investing two percent of their GDP into defense, is relatively close at 1.89 percent. Turkey is closer to paying its share than France, Denmark, Germany, and Canada.

The treaty that gives NATO its name requires member nations to defend each other in the event that one is attacked, meaning America must send military aid if Turkey demands it upon being invaded.

“The Parties agree that an armed attack against one or more of them in Europe or North America shall be considered an attack against them all and consequently they agree that, if such an armed attack occurs, each of them, in exercise of the right of individual or collective self-defence,” the treaty reads.

The treaty also has several provisions that, under Islamist President Recep Tayyip Erdogan, Turkey has flagrantly disregarded. It requires member nations to strengthen their “free institutions” like the press and civil society, which Erdogan has all but shut down in the aftermath of a failed coup against him in 2016. Erdogan has also violated detailed provisions that NATO put in place subsequent to the treaty to keep the alliance functional — most notably, purchasing Russian S-400 missiles that are incompatible with NATO military hardware against the alliance’s rules.

The treaty allows members to leave but does not explicitly provide for expelling a member.