Wrote about this case before: https://www.jehovahs-witness.com/topic/4844148310409216/mark-odonnell-sued-pennsylvanian-congregations-over-eavesdropping-virtual-meeting-between-lawyers-elders
As a matter of general principle, the First Amendment doesn't entitle journalists to wiretap private communications, especially privileged ones involving attorneys. And when an employee shares their access badge with some person and that person uses it to enter a non-public area without proper authorization, it's obviously a trespass, even if they happens to be an activist or whistleblower.
Also, honestly, the information Mark allegedly discovered on that conference call seems to be of little actual public importance - and I don't see him making any claim to the otherwise either in the case papers or in his public statement. It could be a different case if the attorneys instructed elders to, say, shred some documents or bribe officials, but AFAIK they didn't.
Still, it's unclear whether Mark actually violated the law. On the one hand, it doesn't matter whether it was possible for the conference host to identify the stranger and prevent him from participating (and given there were 57 attendees, it was hardly manageable). The really relevant issues in the case are, like, whether Mark had an actual or implied invitation or believed, in good faith, in having such an invitation. Also, if this was a telephone conference call, it would apparently be legal, as far as no device other than a conventional telephone was used and no recording was made, to overhear the conversation. So, it seems to be an open question whether that telephone exception applies to MS Teams and similar conference apps.
There are also other factual and legal issues to be decided, and they mostly have nothing to do with the things discussed on the Internet here and there. For example, the plaintiffs aren't suing for "loss of income", it's blatantly false.