Might federal immigration authorities barge into the Church of the Advocate to arrest the Hernandez family, who have taken sanctuary there to avoid deportation?

In theory, they could. In reality, they probably won't.

As a police arm of the Department of Homeland Security, Immigration and Customs Enforcement, known as ICE, asserts the right to arrest undocumented immigrants wherever they may be found. But ICE guidelines generally steer agents away from action at places designated as "sensitive locations."

Those include schools, doctors' offices, colleges, hospitals and churches, along with weddings, funerals and protest marches.

What's known in immigration circles as one of the "Morton memos," issued in 2011 by then-ICE director John Morton, outlined how enforcement actions at sensitive places should generally be avoided. However, he wrote that actions could be taken if they involved national security, terrorism, or imminent risk of death, violence or physical harm to someone. ICE sets out similar conditions on its website today.

Unstated is that ICE arrests at a church or school risk a public-relations disaster. Imagine the video, in the Hernandez case, of armed officers dragging a mother and four children from a church.

All that offers the Hernandez family some security, as long as they stay inside.

"Congregations are calling for welcome, for sanctuary for the stranger, so for ICE to enter would be a real unveiling of what they're doing," said Peter Pedemonti, director of the New Sanctuary Movement of Philadelphia, an interfaith immigrant advocate that is assisting the family. "It's not about criminality. It's about dragging people down and getting rid of them."

Nationally, some immigrant advocates accuse ICE and its companion agency, Customs and Border Protection, of violating their own policies. This fall Democrats in Congress charged that agents were creating a climate of fear by arresting people near hospitals and churches, if not actually inside them.

In October, federal border patrol agents in Texas stopped an ambulance at a checkpoint, then followed it to a hospital. Agents waited while an undocumented 10-year-old girl underwent surgery, then took her away to a juvenile detention center. Authorities released Rosa Maria Hernandez, who has cerebral palsy, after the American Civil Liberties Union filed a lawsuit.