What should be done about the suspected Nazi leader discovered in Minnesota?

I just heard today that the Associated Press discovered that a suspected leader and co-founder of the Ukrainian Self-Defense Legion has been living in the U.S. for decades. I don’t know much about this group itself, but it sounds like one of many pro-Nazi volunteer groups that arose in German-conquered territories. Although many soldiers in these units were coerced, many others were equally eager to help out with the eradication of Jews in their countries.

According to the AP’s discoveries, this man lied to U.S. Immigration about his wartime service in order to slip into the country. There’s no direct evidence of this individual man’s involvement in atrocities, but the Legion itself is accused of atrocities.

Should he be prosecuted? If so, by whom and for what? Sounds like the U.S., Poland, Germany, and Israel all want to get in on this.