California Governor Gavin Newsom this week vetoed a measure that would have permitted supervised consumption sites — also known as overdose prevention centers — in three cities, Politico reports.

The sites would have allowed individuals to use illegal controlled substances at supervised facilities.

In a letter to members of the California State Senate, Newsom wrote, “The unlimited number of safe injection sites that this bill would authorize — facilities which could exist well into the later part of this decade — could induce a world of unintended consequences. It is possible that these sites would help improve the safety and health of our urban areas, but if done without a strong plan, they could work against this purpose.” He added, “Worsening drug consumption challenges in these areas is not a risk we can take.”

Newsom asked state health authorities to work with local officials to draw up a more detailed and limited pilot program. Rhode Island was the first state to approve supervised injection sites. New York City opened two sites last year.