The Federal Railroad Administration issued the order Thursday. It says violators will be subject to civil penalties and removed from "safety-sensitive" jobs.
The order comes a day after federal investigators announced that a Metrolink engineer sent a text message from his cell phone 22 seconds before his commuter train crashed into a freight train last month. The crash in suburban Chatsworth killed 25 people, including the engineer.
The FRA says the order will be published in the Federal Register in a few days and will take effect 20 days from publication.