And that’s how it should be. If you volunteer to have your DNA on a public database for all to see, no warrant should be needed because you gave permission. If you put it on a private database - search warrant. If you have a sample on file somewhere and they want to look at it - search warrant. Search warrants take less than ten minutes to get by phone in most localities, so there’s no reason for them not to get one.
Parabon utilizes gedmatch for their investigations. Users must opt in for use in law enforcement purposes. If you don’t want your DNA used, don’t opt in.
Btw, the murderer of a childhood friend of mine was identified as a suspect in a string of unsolved murders. Evidence from the crime was uploaded to CODIS, as well as evidence from the unsolved murders. He was convicted in 1 of the cases. These were cases that were unsolved for 30+ years.