Gov. Mark Dayton vetoed an explosive self-defense bill on Monday, saying the lives of police officers could be at risk if citizens are freer to use their guns when they feel threatened.

The governor rejected the measure, saying Minnesota citizens facing threats already have the legal authority to defend themselves and their families. He also cited strong opposition by organizations representing police officers, chiefs of police and county sheriffs.

"When they strongly oppose a measure because they believe it will increase the dangers to them in the performance of their duties, I cannot support it," Dayton said in a veto letter to legislative leaders.

Dayton added that, according to federal figures, there are more than 5 million guns in the state, showing that the "Second Amendment of the U.S. Constitution is properly being supported by lawmakers and law enforcers. ..." He said state law and court decisions "already provide the authorizations for law-abiding citizens to use deadly force to defend themselves or others, either inside or outside of their homes, so long as that force constitutes 'reasonable force.'"

And he noted prosecutors' concern that the law goes too far in justifying such shootings, allowing "anyone to claim that he or she acted reasonably when using deadly force."

Dayton also objected to requiring Minnesota to recognize concealed weapons permits from all states, which he said would "allow people to carry guns here under the considerably lower standards for the issuance of permits of some other states."

The governor waited three days to veto the bill out of respect to the House sponsor, Rep. Tony Cornish, R-Good Thunder.

"It's a sad day in Minnesota for law enforcement," said Cornish. He said Dayton's decision is "mostly the fault of the chiefs and sheriffs and the talking heads, not the rank and file" and he questioned whether those leaders supported gun-owners rights.

Law enforcement opposed

The condemnation of the bill from organizations representing police officers, county sheriffs, police chiefs and prosecutors convinced the DFL governor to veto the bill, which had passed with support from Republicans and outstate DFLers. They argued that the bill could endanger officers by emboldening homeowners to "shoot first" into darkened yards and garages where officers might be in pursuit.

"We're obviously very pleased," said Dennis Flaherty, executive director of the Minnesota Police and Peace Officers Association. "The majority of legislators wanted to say, the hell with law enforcement ... That was disheartening. Nonetheless I'm pleased the governor is concerned about the lives of police officers."

Support for the measure came from the National Rifle Association, which urged members to call Dayton and urge him to sign. Supporters say the bill will return.

"In each state, the police organizations ran around in circles screaming and shouting the sky is falling," said Joe Olson, head of the Gun Owners Civil Rights Alliance in Minnesota. "It hasn't fallen in any state. It wouldn't have fallen in Minnesota."

"The right of self-defense is fundamental, and has been recognized in law for centuries," said the Senate sponsor, Sen. Gretchen Hoffman, R-Vergas. "Today, the governor chose to withhold that right from law-abiding Americans."

Opposition to the bill came from urban legislators and gun-control organizations.

"We are certainly glad that he vetoed the bill," said Joan Peterson, a board member of Protect Minnesota. "This seemed like a bill that was going to allow people to shoot someone as a first impulse rather than as your last impulse."

"Whether it's a kid that enters your yard, or a neighbor having a conflict with another neighbor, or a road-rage incident, this bill broadly expands the use of self defense," said Rep. Michael Paymar, DFL-St. Paul. "I think it's reckless, wrong and unneeded."

Opponents said the "castle doctrine" was misnamed because current law already allows for the use of deadly force in a person's home, or "castle." Both sides agreed there are no known cases on record of Minnesotans being unfairly prosecuted for using deadly force in legitimate self-defense.

Backers: Law needed update

But supporters said the law is unclear and needed to be updated. The bill expanded the right of self-defense to yards, decks and porches as well as to vehicles, boats, motorhomes and tents. In what supporters called the "stand your ground" provision, the bill stated that the person facing the threat "is not required to retreat."

Prosecutors feared that the bill gave too much weight to what the person with a gun "reasonably believes" to be a serious threat, and said it could be used as a defense in violent crimes.

The bill also required Minnesota to recognize a weapons permit issued by any state, even those with no criminal background checks or training requirements. It would have made it harder for police to temporarily remove guns from volatile domestic situations.

The bill received strong support in both houses on final passage -- 40-23 in the Senate and 85-47 in the House. Olson said the measure is "close" to having the support required for an override -- a two-thirds vote in each chamber -- but Cornish said he would not have the votes to do so.

Jim Ragsdale • 651-925-5042 Staff writer Rachel E. Stassen-Berger contributed to this report