Democratic Rep. Rhonda Fields, who represents the district that includes the theater, said the governor had signed "common-sense legislation that reduces gun violence in our communities by keeping guns out of the hands of criminals, domestic violence offenders and the seriously mentally ill."
The shootings led Hickenlooper and other state Democrats to take on the issue of gun control. They succeeded while members of their party stumbled in other states.
Washington state's Democrat-controlled House failed this month to pass a universal background check bill. A bill requiring background checks at gun shows in New Mexico also stalled in that Democrat-led Legislature.
The measures signed by Hickenlooper were the centerpieces of a package of gun bills introduced this session in Colorado.
Under the laws, gun sales and transfers between private parties and purchases conducted online will be subjected to background checks. Ammunition magazines that hold more than 15 rounds will be banned and subject to criminal penalties. Both bills take effect July 1.
Lawmakers debated firearms proposals after the Columbine High School shooting, and began requiring background checks for buyers at gun shows. But nothing they did then was as sweeping as the proposals they took up this year.
Republicans have warned that voters will punish Hickenlooper and other Democrats who voted in favor of the measures.
"I'm telling you, they have overreached, and there are going to be electoral consequences," said Republican Sen. Greg Brophy.
Republicans have said limiting magazine sizes will drive jobs from the state, and ultimately won't prevent criminals from getting larger magazines in other states.
One Colorado-based manufacturer of ammunition magazines disclosed plans to relocate because of the new restrictions.
Some county sheriffs opposed the new background checks, arguing the move is unenforceable and endangers Second Amendment rights.