DENVER  —  The Colorado Supreme Court ruled Monday that a proposal to deny most state services to illegal immigrants cannot appear on the November ballot.

The proposed constitutional amendment, promoted by Defend Colorado Now, violates a state constitutional requirement that initiatives deal with only one subject, the court said in an unanimous opinion.

The measure aimed to decrease public spending for the welfare of illegal immigrants in Colorado and restrict access to administrative services, the ruling said.

Click here to read more in FOXNews.com's Immigration Center.

Proponents, who include former Democratic Gov. Dick Lamm, already had begun gathering petition signatures to get the measure on the ballot. The state Title Board approved the measure's language this spring.

Activist Manolo Ganzales-Estay challenged the measure in court after the Title Board rejected his request to reconsider its approval of the initiative's language.

Fred Elbel, director of Defend Colorado Now, has said if the court found a problem with the measure, he would revise it and supporters would begin gathering signatures anew.

The measure would not stop the state from paying for federally mandated services such as public education or emergency medical care. But Elbel has said it would prevent illegal immigrants from receiving welfare and in-state college tuition.