What do they investigate?
Federal crimes.
The mission of the FBI is to protect and defend the United States against terrorist and foreign intelligence threats, to uphold and enforce the criminal laws of the United States, and to provide leadership and criminal justice services to federal, state, municipal, and international agencies and partners; and to perform these responsibilities in a manner that is responsive to the needs of the public and is faithful to the Constitution of the United States.
That's only if the matter is federal. For instance, a white cop kills a black suspect. They can investigate it for a potential civil rights violation, but outside of federal laws being broken, they don't get involved in the shooting itself. That's up to local authorities. It's the same thing when the Democrats insisted the FBI look into the Kavanaugh case. They refused. It's not their jurisdiction to investigate a claim of a possible local crime that happened 30 years ago. That's up to the city detectives IF they decide to look into the matter, which of course they didn't.
Trump had no authority to send the FBI or anybody into any of those rioting cities. He did however send federal people there to protect a federal courthouse. If they wanted to burn down their city courthouse, the feds would have not interfered.
So are you saying Trump is lying as usual.
Please point out where it states it has to be Federal.
WASHINGTON – President Donald Trump said Wednesday he would "surge" hundreds of federal law enforcement officials into Chicago to help battle gun violence, even as the city's mayor cautioned against unwanted political interference in local operations that has plagued the federal response to sustained civil unrest in Portland, Oregon.
"Today I'm announcing a surge of federal law enforcement into communities plagued by violent crime," Trump said at a White House "law and order" event shrouded in political overtones.
Are you calling Trump a liar?