Police in Washington state and Colorado are trying to teach old dogs to unlearn an old trick.

For as long as dogs have been trained to assist police officers, they’ve been helping make drug busts. But now that the recreational use of marijuana is legal in those two states, officers are in a K-9 quandary.

“We’ll have to look for other indicators,” said Bob Calkins of the Washington State Patrol. “We’ll have to develop cases other ways.”

Adjusting to the new laws, the Washington State Patrol is training new dogs to not react to pot. Existing K-9 units will be phased out. And other agencies are forcing their drug dogs into early retirement and will go without them.