Arizona State Capitol (creative commons)

The bill was one of 28 Brewer signed on Thursday. The Arizona legislature, which wrapped up its legislative session this week, sent numerous bills to the governor's desk to be approved. In all, Brewer approved more than 350 bills while vetoing nearly 30 as of Saturday.

SB-1406, "Allows the governor to build a border fence along the Arizona-Mexico border located on private, state or federal property if permitted," the Arizona Republic reported.

It's unclear how much the bill will cost. The Associated Press reported, "The bill does not specify a cost or make an appropriation but says the state would use donations, inmate labor and private contractors."

Brewer's spokesperson, Matt Benson, declined to comment Friday on whether she planned to invoke it.

On Monday, Brewer sent a letter to President Obama asking him to extend the National Guard's deployment--which ends in June--along the state's border. "I am concerned that when the current mission ends in June, the gains we have made will be immediately lost" Brewer wrote.

Arizona already has a 646-mile fence that covers about 30 percent of the approximately 2,000 mile border between the two countries.