Maryland became the sixth state in as many years to abolish capital punishment Thursday when Gov. Martin O'Malley signed legislation repealing the death penalty.

The new law could face a challenge at the ballot box next year, however. A group that has led successful petition drives in the past was considering whether it would move forward with an expected bid to put the issue to voters in November 2014.

The bill was the first to get the governor's signature during a bill-signing ceremony that included 265 other measures passed during an extraordinarily busy 90-day legislative session through last month. O'Malley, a Democrat, also signed bills to combat "cyberbullying," allow undocumented immigrants to get driver's licenses, expand early voting, reform campaign finance laws and put in place the federal health care law in Maryland.

And he put his signature on another measure to legalize medical marijuana. The law limits distribution to academic medical centers, which will be required to monitor patients and publish their findings.

O'Malley has lobbied lawmakers for seven years to pass the bill to end capital punishment, arguing it is costly and an ineffective deterrent. Under the new law, death sentences will be replaced with life in prison without parole.

To put the issue to voters, MDPetitions.com will have to collect 55,736 signatures by June 30. The same group was instrumental in petitioning three laws to Maryland's ballot last year, including the legalization of same-sex marriage.