The U.S. Attorney's Office Monday announced the arrests of 67-year-old Hsien Tai "Alex" Tsai and his son, 36-year-old Yueh-Hsun "Gary" Tsai.
The machinery includes ones that drill precise holes in metal.
Prosecutors say the U.S. placed a 2009 ban on the father from doing any business in the U.S. as suspicions around him grew. But the complaint says he continued trying to export machines from the U.S. with his son's help.
"When you look at the actual evidence it really amounts to a rather benign business transaction between a son and his father," said Tsai's defense attorney Ted Poulos.
Prosecutors say the father was arrested Wednesday in Estonia. The son was arrested the same day at his home in Glenview, Illinois.
Gary Tsai's wife left court without comment after posting $500,00 bond, including the couple's Glenview home.
Tsai's attorney questions how the sale of simple machinery can be considering supporting the productions of 'weapons of mass destruction."
"When you look at the complaint, you'll see my client's conduct as alleged really involves buying 40-year-old drilling equipment," Poulos said.
- DOWNLOAD: Read the Criminal Complaint against Hsien Tai Tsai
- DOWNLOAD: Read the Criminal Complaint against Yueh-Hsun Tsai
Federal prosecutors do not allege that the machinery ended up in North Korea - just that those who the Glenview man sold it to had been middlemen for the regime in years past.
The transactions took place a few years before the recent spike in tension with North Korea.
The Associated Press contributed to this report.