I am no expert on the whole Mueller special counsel operation, or the FBI raid on Trump's personal attorney. Nor on what, if anything, justifies confiscating privileged attorney-client communications.
That said, there is substantial reason to believe Andrew C. McCarthy who writes for National Review is an expert on all of those matters. He spent 20 years working as a prosecutor for the very Southern District of New York branch of the Justice Department which ordered the FBI raid.
See McCarthy's take on what serious stuff had to be alleged to get judicial permission to raid Cohen's office and quarters. Given the collective clout attorneys have, it's likely the level of proof is substantially higher than that for a FISA warrant, which has been demonstrated to be susceptible to flimflammery.
Having read McCarthy's entire column, I take a less sanguine view of the FBI raid on Cohen. It could get ugly for Trump.
