>since they now know (or should know)

but can you hold them to that in any manner or does each officer need to be told officially and continue to plead ignorance of the law until they are in some documented way informed of it? can you plead ignorance of the law if you know it's not legal to dump all traffic from a cell phone tower but no one said that it's not legal to dump all the traffic from a web server (assuming for the sake of argument the obv interpretation that this ruling applies to all data stores that contain data from multiple people)? Every time you need to violate the constitution can you just have the new guy do it? Does declaring this illegal actually do anything to protect the rights of people who did nothing wrong and had their data seized and pored over by police anyway?

>> Does declaring this illegal actually do anything to protect the rights of people

Yes, next time they do it the data cannot be used in court as it was already declared anti-constitutional by that Circuit and good faith argument cannot be used. Good faith and not knowing the law are different; good faith can be used when the law is not clear enough and there was no rule to clarify.

It happens very often with 2A restrictions that are overturned by courts, but they are in effect for years and when they are repelled by courts then similar laws are passed just to be repelled years later, but during all the years there is an anti-constitutional law in place with prohibitions. So police cannot do cell searches, but local governments can enact anti-constitutional laws with intention and wipe rights successfully, for example laws that mandates telecom companies to provide the data to the police.