When did they pass this little nugget?

It seems that the Federal Government has formally decreed that all persons who are arrested by a Federal law enforcement agency will have to submit a DNA sample for criminal analysis, for both now and forever in the future. Not convicted, not even charged, mind you, but simply arrested. There goes any last remnant of "innocent until proven guilty", as they apparently wish to go fishing with all arrestees' genetic information to see what they can come up with.

Here's the real problem, if you ask me:

"There are dozens of federal law enforcement agencies, ranging from the FBI to the Library of Congress Police"

Why does every last little government department need its own police force? Why can't Library of Congress workers simply call the D.C. Police if someone is being disruptive, or damaging property?

What happens to the DNA samples if one is found innocent, or the charges against them dropped?

"If a person is arrested but not convicted, he or she can ask the Justice Department to destroy the sample".

Good luck with that. It says that one can ask; it doesn't say anything about the government having to say "yes" if they don't feel like it. My guess? That they simply won't ever feel like it, and people with overdue books, or flash-mobbers who get rousted at Federal memorials (see below) are going to have to open wide to get their cheeks swabbed.