CHICAGO (CBS) — Calling it a “very important public safety measure for our state,” Gov. Pat Quinn is proposing a ban on assault weapons in Illinois.

The governor is using his amendatory veto power to include the ban in a bill related to ammunition sales.

It is now up to lawmakers to accept his changes or reject them.

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“This morning, I … vetoed a bill that arrived at my desk in order to give the legislature an opportunity to put into law a ban on assault weapons in Illinois and a ban on large capacity ammunition,” Quinn said.

“It’s very clear that these particular weapons are not designed to do anything but to have human targets.”

His proposal will face big hurdles, even after the massacre at a Colorado movie theater renewed national debate about assault weapons.

State Sen. Kirk Dillard (R-Hinsdale) said: “If the governor is really serious about passing an assault weapons ban in Illinois he needs to sit down with–as distasteful as it may seem to some–with the state rifle association and see what definitions they can live with.”

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Cook County’s ban has undergone legal challenges. The Illinois Supreme Court this year reversed lower-court rulings that found the ban constitutional, sending it to trial court.

Other gun-control measures have also failed in the General Assembly.