Comment by TheSkeptic

"BART, which has its own police force, must be held to constitutional standards."

This sounds nice, but do you actually know what those Constitutional standards are?

First, as you seem to recognize, the area in which cell phone service was disrupted is what is considered a "nonpublic forum." The government has significant latitude to restrict speech in nonpublic forums, especially when the restriction is related to the function of that forum. Here, BART shut down cell phone service because it was informed that a group of "protesters", which had caused disruption to BART service in the past, was going to use cell phones to organize another disruption. According to reports, cell phones were to be used to communicate the locations of BART police officers to maximize the mob's ability to disrupt service.

Second, not all speech is due protection under the First Amendment. There is protected speech, and unprotected speech.Speech designed to incite violence or create a breach of the peace is not protected. There is substantial case law on this. Here, based on tweets like "We are going to show BART (@SFBART) how to prevent a riot #OpBART" and the past actions of this particular group of "protesters", it is clear that BART had a compelling reason to temporarily shut down cell phone service in its stations.

Finally, in this case, BART did not prevent this group of "protesters" from expressing ideas. It simply restricted, temporarily, a particular mode of delivery.

What about those who weren't planning to use their cell phones to incite a riot? Again, there is more latitude to restrict speech in nonpublic forums, and any restrictions here were content-neutral, narrowly drawn in terms of time, place and manner, and were for a compelling purpose (protecting public safety).

Bottom line: this is only a Constitutional issue if you have no understanding of the Constitution and First Amendment case law.