Facebook shut down the pages of state-authorized medical-marijuana dispensaries this week in Colorado and elsewhere, including today in Arizona.

"I don't fully understand it, and I can't explain it," says J.P. Holyoak, principal of Arizona Natural Selections in Phoenix. "We got a notice this morning saying our account had been suspended. They provided no explanation."

Holyoak is also chairman of the Campaign to Regulate Marijuana Like Alcohol in Arizona, which is on track to put an adult-use legalization measure on the ballot in Arizona. Political or public policy pages like those for the Arizona campaign haven't been affected.

Many other Arizona dispensary sites also are down, displaying the dry message, "Sorry, this content isn't available right now."

Kim Prince of Proven Media and co-chair of the Oakland, California-based Women Grow, a cannabis educational and policy group, says the Facebook shutdown is a huge concern for hundreds of dispensary operators in Colorado, too.

"These are licensed dispensaries that are 100 percent state-compliant," Prince says. "Crazy stuff."

Holyoak calls the development "odd."

"Marijuana is gaining greater and greater acceptance across the country every day — you'd think these things would be loosening up, not tightening up."

Sean Parker, a former Facebook president, has thrown his support behind a California legalization initiative, Holyoak notes.

Facebook has declined to comment about the matter.

Prince says a growing list of Arizona dispensary pages representing tens of thousands of patients have been taken down. But inexplicably, some remain active, like the page for Uncle Herbs in Payson. (UPDATE: That page and several others that had remained active as of Thursday evening are now also off-line.)

The Facebook action "cuts off patient access, is detrimental to the dispensary brands," Prince says. "It is unethical behavior — it impedes on freedom of speech and Internet laws."

It seems to have started in New Jersey. As NJ Advance Media reported:

"Officials from Breakwater Wellness and Treatment Center in Cranbury and Compassionate Sciences Alternative Treatment Center in Bellmawr said their home pages were shut down Tuesday. When they tried to use their home page, they found an electronic message that said: "We remove any promotion or encouragement of drug use. Your page is currently not visible on Facebook. It looks like content on your page does not follow the Facebook Community Terms and Standards."