Now that the Legislature has passed a bill that would allow gun owners to use deadly force anywhere they feel threatened, only Gov. Mark Dayton can prevent it from becoming law. He shouldn't hesitate to reject it.

Known as an expanded version of the "castle doctrine," the bill would allow Minnesotans to shoot to kill even if they aren't at home. The state's current castle law already allows citizens to use deadly force in their homes to protect themselves.

But the proposed law, more appropriately called the "shoot first" bill by opponents, would let gun owners fire at people they perceive as threats -- without the expectation that they should first attempt to avoid trouble if possible.

Minnesota doesn't need this change. The state already has a conceal-and-carry law, and citizens who choose to arm themselves can already use firearms for protection anywhere within reasonable limits.

For years, shoot-first expansion has been among the top legislative priorities for the National Rifle Association. The organization believes that gun owners should have unfettered rights to defend themselves whenever and wherever they feel threatened.

That's part of the problem: Defining a threat can be very personal -- and mistakes can be deadly. Some gun owners may feel nervous because of the way a group of youths is dressed. Others might find members of a different race or culture to pose a threat.

And what about those occasions when a person hears a noise and worries that it could be someone who would do them harm? Then there's the issue of defending one's life vs. protecting property.

The proposed law allows deadly force to be used against anyone who enters a garage, for example, "by stealth or force." That means a homeowner could injure someone or take a life over the theft of a car, bicycle or lawn mower. In a civilized society, the only rationale for shooting or killing someone should be real self-defense in protecting life and limb.

As Dakota County Attorney James Backstrom pointed out in a Feb. 15 commentary on these pages ("A bill for the trigger-happy? Bull's-eye"), the modified law would allow people to shoot first and ask questions later whenever they believed they were threatened, regardless of how a reasonable person would have responded under the same circumstances.

It speaks volumes that Backstrom and most other state and national prosecutors, as well as law enforcement groups, oppose the proposal. They're on the front lines and understand that deadly force should be the last resort.

Rep. Tony Cornish, R-Good Thunder, has supported expanded castle legislation for years, arguing that the change would codify that law-abiding people "have the brains" to understand the seriousness of deadly force.

Cornish, a former police chief, believes the bill is a logical extension of current law and that the change is needed because citizens need to know that they won't be prosecuted for defending themselves.

But Cornish can't point to a single case in Minnesota in which someone acting in self-defense was convicted of anything or sent to jail. The governor nixed a similar "shoot first" bill last year, and he should use his veto pen again on this dangerous piece of legislation.