A legal issue could keep several fighters, including Mauricio “Shogun” Rua and Alistair Overeem, from competing at UFC on FS1: Shogun vs. Sonnen in August.

According to a report by the Boston Herald, a Massachusetts law bars foreign-born fighters from fighting in the state without a Social Security number.

“This law has been in existence since we legalized mixed martial arts in the commonwealth of Mass­achusetts,” said Terrell Harris, spokesman for the state Department of Public Safety. “It’s been brought to the attention of the UFC more than a few times since we legalized the fighting here. But they’ve chosen basically to ignore the law and hope that they could skirt it somehow.”

Previously, the UFC held an event in Massachusetts in 2010 with Demian Maia and Andre Winner fighting. Both are foreigners, and neither had issues competing.

Rua is expected to face Chael Sonnen in the main event, while Overeem is set to battle Travis Browne.