An Illinois lawmaker wants gun owners to shell out extra taxes in order to finance a new grant program for trauma centers, a move firearms advocacy groups say amounts to a "sin tax" on law-abiding hunters and target shooters.

State Rep. Kelly Cassidy, in a bill introduced earlier this month, proposed a 2 percent surtax on ammunition. The proceeds would go toward a "high-crime trauma center grant fund," which would then send the tax money to trauma centers in "high-crime areas."

The idea is to begin to offset the high cost of gun violence. Mark Walsh, campaign director for the Illinois Campaign to Prevent Gun Violence, told FoxNews.com that cost often ends up being shouldered by these urban trauma centers.

"(The money would go) into communities here in Illinois that have been damaged with gun violence," he said. "I think it's a legitimate way to pursue funding."

But Richard Pearson, director of the Illinois State Rifle Association, said the bill effectively saddles gun owners -- hunters, target shooters and those who own firearms for self defense -- as a whole with the cost of gang violence in high-crime areas like Chicago.

"We aren't causing the problem. They are," Pearson said. "It's an attack on firearm owners and their rights. ... They think that because we like to target shoot and hunt, we're bad people, and we should pay for all the ills of the city of Chicago."

Since gun owners in Illinois have to have a special ID card which requires a background check to obtain, Pearson said those committing crimes of gun violence aren't likely to be paying much into the proposed tax fund.

"They're not buying their ammunition (legally). They're not paying any part of the tax. They're getting their stuff illegally," he said.

He estimated a typical box of ammo runs for about $25 in Illinois, meaning the average tax per box would be about 50 cents.

Cassidy, a Democrat who represents a district in the North Side of Chicago, did not return a request for comment.

Her proposal would exempt ammunition purchases by the state's Department of Natural Resources.

All the surtax proceeds from other ammo sales would go toward the grant fund.

The National Rifle Association is also opposed to the bill. Spokeswoman Stephanie Samford said "law-abiding citizens should not be saddled with a tax on ammunition to pay for the acts of violent criminals."

"This sends a message that responsible gun owners are somehow responsible for violent crime, which is certainly not true," she said.