The case you identify is not unique. For example, the Unitarian church in Denver has done much the same thing.
There is not a legal right to sanctuary in a church. But, as a manner of law enforcement discretion and public relations and customary traditions of law enforcement respect for churches that long predate the formation of the USA, law enforcement routinely acts as if there was a right to sanctuary in churches (in the absence, for example, of an active shooter situation or a hostage crisis or a kidnapping with a missing victim). I am not aware of any case in which immigration officials have taken push to shove and breached a claim of sanctuary by a church protecting an illegal immigrant in a church.
In England, where there was an established church, the established Anglican Church historically did have a right to intervene in certain ways in the criminal justice process (e.g. the "privilege of clergy").
UPDATE (February 21, 2017): My original answer was not entirely correct so I am updating this post. It turns out that in 2011 that Immigrations and Customs Enforcement made what was previously a mere custom into an official policy, something I was not previously aware of.
U.S. Immigration and Customs Enforcement (ICE) and U.S. Customs and
Border Protection (CBP) have made available Frequently Asked Questions
(FAQs) to supplement existing guidance concerning enforcement actions
at or focused on sensitive locations and clarify what types of
locations are covered by these policies.
The ICE and CBP sensitive locations policies, which remain in effect,
provide that enforcement actions at sensitive locations should
generally be avoided, and require either prior approval from an
appropriate supervisory official or exigent circumstances
necessitating immediate action. DHS is committed to ensuring that
people seeking to participate in activities or utilize services
provided at any sensitive location are free to do so without fear or
hesitation.
Do the Department of Homeland Security's policies concerning
enforcement actions at or focused on sensitive locations remain in
effect?
U.S. Immigration and Customs Enforcement (ICE) and U.S. Customs and
Border Protection (CBP) have each issued and implemented policies
concerning enforcement actions at or focused on sensitive locations.
The ICE Sensitive Locations Policy and the CBP Sensitive Locations
Policy remain in effect, and these FAQs are intended to clarify what
types of locations are covered by those policies.
What do the Department of Homeland Security policies require for
enforcement actions to be carried out at sensitive locations?
The policies provide that enforcement actions at or focused on
sensitive locations such as schools, places of worship, and hospitals
should generally be avoided, and that such actions may only take place
when (a) prior approval is obtained from an appropriate supervisory
official, or (b) there are exigent circumstances necessitating
immediate action without supervisor approval. The policies are meant
to ensure that ICE and CBP officers and agents exercise sound judgment
when enforcing federal law at or focused on sensitive locations, to
enhance the public understanding and trust, and to ensure that people
seeking to participate in activities or utilize services provided at
any sensitive location are free to do so, without fear or hesitation.
What does the Department of Homeland Security mean by the term
“sensitive location”?
Locations covered by these policies would include, but not be limited
to:
Schools, such as known and licensed daycares, pre-schools and other
early learning programs; primary schools; secondary schools;
post-secondary schools up to and including colleges and universities;
as well as scholastic or education-related activities or events, and
school bus stops that are marked and/or known to the officer, during
periods when school children are present at the stop; Medical
treatment and health care facilities, such as hospitals, doctors’
offices, accredited health clinics, and emergent or urgent care
facilities; Places of worship, such as churches, synagogues, mosques,
and temples; Religious or civil ceremonies or observances, such as
funerals and weddings; and During public demonstration, such as a
march, rally, or parade.
What is an enforcement action?
An enforcement action covered by this policy is any action taken by
ICE or CBP to apprehend, arrest, interview, or search an individual,
or to surveil an individual for enforcement purposes.
Actions not covered by this policy include activities such as
obtaining records, documents, and similar materials from officials or
employees, providing notice to officials or employees, serving
subpoenas, engaging in Student and Exchange Visitor Program (SEVP)
compliance and certification visits, guarding or securing detainees,
or participating in official functions or community meetings.
Will enforcement actions ever occur at sensitive locations?
Enforcement actions may occur at sensitive locations in limited
circumstances, but will generally be avoided. ICE or CBP officers
and agents may conduct an enforcement action at a sensitive location with
prior approval from an appropriate supervisory official, or if the
enforcement action involves exigent circumstances.
When may an enforcement action be carried out at a sensitive location
without prior approval?
ICE and CBP officers may carry out an enforcement action at a
sensitive location without prior approval from a supervisor in exigent
circumstances related to national security, terrorism, or public
safety, or where there is an imminent risk of destruction of evidence
material to an ongoing criminal case.
When proceeding with an enforcement action under exigent
circumstances, officers and agents must conduct themselves as
discreetly as possible, consistent with officer and public safety, and
make every effort to limit the time at or focused on the sensitive
location.
Are sensitive locations located along the international border also
protected?
The sensitive locations policy does not apply to operations that are
conducted within the immediate vicinity of the international border,
including the functional equivalent of the border. However, when
situations arise that call for enforcement actions at or near a
sensitive location within the immediate vicinity of the international
border, including its functional equivalent, agents and officers are
expected to exercise sound judgment and common sense while taking
appropriate action, consistent with the goals of this policy.
Examples of operations within the immediate vicinity of the border
are, but are not limited to, searches at ports of entry, activities
undertaken where there is reasonable certainty that an individual just
crossed the border, circumstances where DHS has maintained
surveillance of a subject since crossing the border, and circumstances
where DHS is operating in a location that is geographically further
from the border but separated from the border by rugged and remote
terrain.
Are courthouses sensitive locations?
Courthouses do not fall under ICE or CBP’s policies concerning
enforcement actions at or focused on sensitive locations.
Where should I report a DHS enforcement action that I believe may be
inconsistent with these policies?
There are a number of locations where an individual may lodge a
complaint about a particular DHS enforcement action that may have
taken place in violation of the sensitive locations policy. You may
find information about these locations, and information about how to
file a complaint, on the DHS, CBP, or ICE websites.
You may contact ICE Enforcement and Removal Operations (ERO) through
the Detention Reporting and Information Line at (888)351-4024 or
through the ERO information email address at [email protected],
also available at https://www.ice.gov/webform/ero-contact-form. The
Civil Liberties Division of the ICE Office of Diversity and Civil
Rights may be contacted at (202) 732-0092 or
[email protected].
You may contact the CBP Information Center to file a complaint or
compliment via phone at 1 (877) 227-5511, or submit an email through
the website at https://help.cbp.gov.
The policy is drafted in a manner that it doesn't actually prohibit enforcement in a sanctuary, even in the absence of exigent circumstances, but it does call for a process to be followed if this is done, and discourages doing so without prohibiting this action.