Throwing his liberal supporters a bone.

Washington (CNN) — Attorney General Eric Holder, a longtime target of Republicans who have tried to force him out of office, now faces the prospect of angering liberal supporters when the Justice Department decides whether to file federal charges in the Trayvon Martin killing.

Civil rights groups are planning nationwide vigils, and more than a million people support an online petition drive calling for admitted shooter George Zimmerman to face federal charges in the February 2012 killing.

Holder confronted that political pressure Tuesday in a speech to the NAACP, which is conducting the petition drive.

He repeated his pledge for a full investigation of Martin’s death in the aftermath of Zimmerman’s acquittal on murder and manslaughter charges by a Florida court, but was careful to avoid any promise or hint of federal charges.

Instead, Holder took aim at “stand your ground” laws like the one in Florida that provides the right to respond with deadly force if attacked outside their home. Those laws “senselessly expand the concept of self-defense and sow dangerous conflict in our neighborhoods,” he said.

“By allowing — and perhaps encouraging — violent situations to escalate in public, such laws undermine public safety,” Holder said in his first public comment on self-defense legislation passed in some form in more than 30 states.

Zimmerman’s lawyers didn’t invoke Florida’s “stand your ground” law in court, but it was included in the instructions to the jury that acquitted him. Holder’s focus Tuesday on a broader legal issue avoided the difficult decision he faces over whether to bring federal criminal charges.