Gov. John Hickenlooper said Wednesday he opposes Amendment 64, a November ballot measure that would legalize limited possession of marijuana for adults in Colorado.

“Colorado is known for many great things — marijuana should not be one of them,” Hickenlooper said in a statement. “Amendment 64 has the potential to increase the number of children using drugs and would detract from efforts to make Colorado the healthiest state in the nation. It sends the wrong message to kids that drugs are OK.”

The announcement drew praise from Amendment 64’s opponents, who say marijuana legalization would harm Colorado’s children and businesses.

“We want to thank Gov. Hickenlooper for doing the right thing and opposing Amendment 64 today,” Laura Chapin, a spokeswoman for No on 64, said in a statement. Chapin also writes a column for The Denver Post.

But Amendment 64’s backers said Hickenlooper, a former microbrewery owner, was hypocritical to oppose marijuana.

“After building a personal fortune by selling alcohol to Coloradans, he is suddenly concerned about the health of his citizens and the message being sent to children,” proponent Mason Tvert said in a statement. “We certainly hope he is aware that alcohol actually kills people.”

Hickenlooper’s announcement was the second blow for Amendment 64’s supporters Wednesday.

Earlier, an effort by the measure’s proponents to convince a judge to change the language in the state-produced voter guide about the initiative failed.

Denver District Chief Judge Robert Hyatt ruled the courts do not have the authority to make changes to the guide, which is known as the blue book. The ruling means the guide will be published without three sentences arguing in favor of the initiative.

Hyatt said previously decided cases show that Colorado courts have “a strong tradition” of respecting the separation of powers and not interfering with legislative functions.

“The judiciary may not substitute its judgment for the judgment of the legislature,” he said.

Amendment 64 would legalize possession of up to an ounce of marijuana for adults. It would also allow for commercial pot shops, which cities could ban.