The Veterans’ Memorial Preservation Act protects some monuments, but not all.

President Donald Trump took to Twitter Tuesday to say that he had “authorized the Federal Government to arrest anyone who vandalizes or destroys any monument, statue or other such Federal property in the U.S. with up to 10 years in prison, per the Veteran’s Memorial Preservation Act.”

On the White House South Lawn, preparing to board Marine One for his trip to Arizona, Trump thanked police for their work Monday night stopping the protesters, whom the president referred to as “vandals, hoodlums, anarchists and agitators.”

“Last night we stopped an attack on a great monument of Andrew Jackson and Lafayette Park,” Trump told reporters, adding that “numerous people” are already in jail and more are going “today.”

However in relation to the Veterans’ Memorial Preservation Act, federal law enforcement already had this authority and they have for a while.

The act was passed in 2003 in the wake of a rash of vandalism incidents at military cemeteries in Hawaii and elsewhere.

Bradley P. Moss, partner at the Washington, D.C., law office of Mark S. Zaid, P.C., told ABC News that federal law enforcement already had that authority and that President Trump’s tweet is “redundant and irrelevant because it doesn’t change what they can and will do.”

The act itself is written as follows:

“Whoever, in a circumstance described willfully injures or destroys, or attempts to injure or destroy, any structure, plaque, statue, or other monument on public property commemorating the service of any person or persons in the armed forces of the United States shall be fined under this title, imprisoned not more than 10 years, or both.”

Statues commemorating historical figures such as Christopher Columbus and Francis Scott Key would not apply under this act, however, since they never served in the armed forces.

If a crime is committed that violates this act, the prosecution would be authorized under the law passed by Congress; the president directs enforcement of that law.

However, in reference to the incidents on Monday night, Moss said that “if they were to deface a statue that was dedicated to memorializing Andrew Jackson’s military service, it’s entirely possible that the arrest from last night will invoke this law. It’s not clear that the law was specifically applied to that statute, but it’s possible.”

Lastly, Moss said the president cannot do anything more than what law enforcement — in this case the United States Park Police (USPP) — are already prepared to do. And that goes for prosecutors as well.

“Local prosecutors who are going to bring charges, if any, against those who were arrested last night, are aware of what they can and can’t invoke,” Moss said. “They didn’t need the president’s tweets to remind them.”