Courtesy NBC News

By Pete Williams and Tracy Connor, NBC News

Attorney General Eric Holder took aim Tuesday at "Stand Your Ground"-style laws — such as the one that figured into the George Zimmerman case — saying they may encourage violence and "undermine public safety."

"It's time to question laws that senselessly expand the concept of self-defense and sow dangerous conflict in our neighborhoods," Holder said in a speech to the NAACP. "These laws try to fix something that was never broken.

"There has always been a legal defense for using deadly force if — and the 'if' is important — if no safe retreat is available. But we must examine laws that take this further by eliminating the common sense and age-old requirement that people who feel threatened have a duty to retreat, outside their home, if they can do so safely.

"By allowing — and perhaps encouraging — violent situations to escalate in public — such laws undermine public safety. The list of resulting tragedies is long and, unfortunately, has victimized too many who are innocent.

"It is our collective obligation. We must 'stand our ground' to ensure that our laws reduce violence and take a hard look at laws that contribute to more violence than they prevent."

More than 20 states have so-called "Stand Your Ground" laws, which became the subject of national debate after Zimmerman, 29, said he fatally shot an unarmed Trayvon Martin, 17, in self-defense on Feb. 26, 2012, in Sanford, Fla.

Zimmerman did not invoke Florida's "Stand Your Ground" law and ask for an immunity hearing before the trial, but the jury that acquitted him received instructions that borrowed language from the statute, specifying that if "he was attacked in any place where he had a right to be, he had no duty to retreat and had the right to stand his ground and meet force with force."

George Zimmerman leaving the courtroom after being found not guilty on July 13.(Joe Burbank via EPA)

Holder's comments, in a long-planned address to the civil rights group, came as the Rev. Al Sharpton, president of the National Action Network and an MSNBC host, announced plans for a campaign by clergy to get the laws off the books. Sharpton is also urging Holder to "aggressively" pursue a federal civil-rights investigation of Zimmerman.

Although the NAACP speech marked Holder's first comments on "Stand Your Ground," he has addressed the Zimmerman case numerous times.

In April 2012, he said there would be a "high bar" to make it a Justice Department case.

"For a federal hate crime we have to prove the highest standard in the law. You know, something that was reckless, that was negligent does not meet that standard. We have to show that there was specific intent to do the crime with the requisite state of mind," he said.

After Saturday's verdict, the Justice Department released a statement confirming the investigation it launched in 2012 was still open.

"Experienced federal prosecutors will determine whether the evidence reveals a prosecutable violation of any of the limited federal criminal civil rights statutes within our jurisdiction, and whether federal prosecution is appropriate in accordance with the Department's policy governing successive federal prosecution following a state trial," it said.

On Monday, speaking at a luncheon by a predominantly black sorority, Holder called Martin's death "unnecessary" and praised the teen's mother and father for their dignity in the face of "pain that no parent should have to endure."

Although Holder said he and the agency share "concern" about the case, he gave no indication that federal charges against Zimmerman are forthcoming.

Indeed, several legal experts say it would be surprising if the feds file a criminal case under a four-year-old federal hate-crime statute making it a crime to to cause "bodily injury to any person ... because of the actual or perceived race" of the victim.

"Usually when you have a successful prosecution, you have multiple statements made by the defendant about the victim's race while the defendant is attacking, or you have a group of people that went out looking for someone of a particular race to attack," said Samuel Bagenstos, a former top official in the Justice Department's Civil Rights Division.

"Proving what's on somebody eles's mind is as difficult thing to do in the law as possible."

Martin's supporters have said Zimmerman, a neighborhood watch volunteer who is of white and Hispanic descent, had a history of calling police to report "suspicious" black males in his gated community.

During a call to a non-emergency line when he spotted Martin walking around, he only mentioned he was black when asked about his race by the dispatcher. He also referred to "f---ing punks" and complained, "These guys always get away."

Defense lawyer Mark O'Mara has said race played no factor in the confrontation between Zimmerman and Martin. He said his client's background shows that he is a "non-racist."

The only juror to speak about the deliberations and acquittal told CNN this week that no one on the six-woman panel believed race played a role.

George Zimmerman has sued NBC Universal for defamation. The company strongly denies the allegation.