In February, D.C. police up and decided that they would watch video feeds from their surveillance cameras live, in real time. Chief Cathy Lanier told the Washington Post she thought her department under-utilized its cameras. “I thought, ‘Why the heck aren’t we watching them?'” she said.

Here’s why: The law suggests that you aren’t supposed to watch. Check out this tidbit from Title 24, Chapter 25 of the D.C. Municipal Regulations:

When CCTV is used to combat crime, recordings may be passively monitored, meaning that the video feeds may not be monitored in real time, and recordings may be viewed by MPD personnel where there is reason to believe that the viewing may help solve a crime.

Metropolitan Police Department spokeswoman Traci Hughes says the law doesn’t forbid real-time watching.

“The statute says may, not shall,” Hughes told the Washington City Paper. “It’s a matter of legal construction. Because the statute says may, it does not prohibit the Chief from actively monitoring the cameras.”

Art Spitzer, legal director of the local ACLU, doesn’t like Hughes’s reasoning.

“I don’t think any judge would buy her argument,” Spitzer writes in an email. “There is a difference between may and shall, but ‘may not’ means ‘no.'”