A little-noticed provision in the 2,232-page government spending bill passed last week bans U.S. arms from going to a controversial ultranationalist militia in Ukraine that has openly accepted neo-Nazis into its ranks.

House-passed spending bills for the past three years have included a ban on U.S. aid to Ukraine from going to the Azov Battalion, but the provision was stripped out before final passage each year.

This year, though, the $1.3 trillion omnibus spending bill signed into law last week stipulates that "none of the funds made available by this act may be used to provide arms, training or other assistance to the Azov Battalion."

"White supremacy and neo-Nazism are unacceptable and have no place in our world," Rep. Ro Khanna (D-Calif.), an outspoken critic of providing lethal aid to Ukraine, said in a statement to The Hill on Tuesday. "I am very pleased that the recently passed omnibus prevents the U.S. from providing arms and training assistance to the neo-Nazi Azov Battalion fighting in Ukraine."

The United States has been aiding and training Ukrainian forces in their fight against Russian-backed separatists since 2014, and recently expanded that aid to include arms. The omnibus includes about $620.7 million in aid for Ukraine, including $420.7 million in State Department and foreign operations funds and $200 million in Pentagon funds.

The Azov Battalion was founded in 2014, and its first commander was Andriy Biletsky, who previously headed the neo-Nazi group Patriot of Ukraine. Several members of the militia, which has been integrated into the Ukrainian National Guard, are self-avowed neo-Nazis.

But a spokesman for the group has defended it, telling USA Today in 2015 that only 10 to 20 percent of recruits are neo-Nazis and that those people do not represent the official ideology of Azov.

It's unclear how much, if anything, from the United States has gone to Azov in the past.

"The State Department should pressure Kiev to dissociate itself with this group and investigate whether any of our weapons or training have already been provided to them," Khanna said in his statement. "This is just one of many reasons why lawmakers should be concerned about channeling huge amounts of weapons into this volatile conflict zone."

Last year, online posts by the militia's news service showed members testing U.S.-made grenade launchers at a firing range. The posts have since been deleted, and the Ukrainian National Guard insisted in a January statement that the grenade launchers were not in Azov's possession.

U.S. officials have said vetting required under the so-called Leahy Law already prevents the United States from aiding Azov. The Leahy Law bans U.S. aid from going to groups when the "secretary of State has credible information that such unit has committed a gross violation of human rights."

But proponents of a ban specific to Azov say the Leahy Law did not preclude it from getting aid, since the secretary of State has never made such a determination about the group.