GREEN BAY, Wis. -

A government attorney is trying to persuade a federal judge in Green Bay to toss out U.S. Sen. Ron Johnson's lawsuit challenging rules forcing congressional members and their employees to seek government-subsidized health insurance through small business exchanges.

U.S. Justice Department attorney James Luh told U.S. District Judge William Griesbach on Monday that Johnson can't sue because he hasn't shown how the rules have caused him any injury.

Johnson's attorney, Rick Esenberg, says Johnson is suffering an injury because he must decide which staff members should go through the exchanges. Esenberg also argued the rules force Johnson into illegal activity because he and his staffers aren't eligible for small business exchanges since they work for a huge employer.

"If I do nothing then all my staff continues to hold onto their federal employee health benefits, which the Affordable Care Act explicitly made clear was not supposed to happen," Johnson said.

It's unclear when Griesbach might rule.