It won't be. That won't come close to holding up in terms of legal challenges. And it won't take long to get challenged legally. It's not a close debate, it's not a maybe situation, it won't come close to holding up.

The LAPD may attempt to use that angle - probable cause - in some isolated circumstances short-term, before there's anything specifically legally blocking them, if they're going to get aggressive with trying to procure social media information from people. They would know that refusal to provide social media details as probable cause can't hold up legally to a challenge and they'll risk getting barred from asking entirely, so they'll likely be careful about who they try that tactic on.