In a pre-emptive release, Sheriff Joe Arpaio said his office was bracing for "massive numbers of protesters" at the Fourth Avenue Jail, where all Valley agencies bring their arrestees for booking. He has canceled public visitation at the jail and put all inmates on a 24-hour lockdown, beginning at 9 a.m. as a security measure. He has also beefed up security measures for himself and his staff.

An old man takes part in a demonstration against Arizona's controversial Senate Bill 1070 immigration law in downtown Phoenix, Arizona, the United States, July 29, 2010. The immigration law takes effect in Arizona on Thursday with some key portions blocked by U.S. District Court Judge Susan Bolton. [Qi Heng/Xinhua]

By early afternoon, most of the activities were centered on the Fourth Avenue Jail, a primary booking location for felony arrests in Maricopa County. A total of 23 people were arrested for blocking a public thoroughfare, Sheriff Joe Arpaio said at a press conference Thursday afternoon. Among the detained people are some media members who were covering the event.

The Rev. Susan Frederick-Gray of the Unitarian Universalist Church in Phoenix said she came to the jail because "I am standing for human rights. Not one more person, not one more mother, not one more grandfather will be taken from their family."

The remnants of the law that were not blocked took effect at 12: 01 a.m.. Arizona Governor Jan Brewer's legal team have filed an expedited appeal of the judge's order early Thursday afternoon.

These blocked provisions include:

-- The portion that requires officers to check a person's immigration status if there's reasonable suspicion they're in the country illegally;

-- The portion that creates a crime of failure to apply for or carry "alien-registration papers;"

-- The portion that makes it a crime for illegal immigrants to solicit, apply for or perform work;

-- The portion that allows for a warrantless arrest of a person where there is probable cause to believe they have committed a public offense that makes them removable from the United States.