A Democrat legislator from Massachusetts tipped off suspected criminal aliens regarding a coming ICE raid.  The fact that she did so, and how she did so, can be considered a criminal act.  Attorney General Sessions can prosecute.  Here is how. 

As the Department of Justice Criminal Resource Manual for federal prosecutors apprises, the criminal law "makes it an offense" for anyone to "encourage" an alien to "reside" in the United States, when "knowing" the person's residence "will be in violation of law."  "Aiding and abetting" such encouragement or illegal residence is also a federal crime.  The law imposes a term of imprisonment up to five years in federal prison.

The statute reads as follows: a person violates 8 USC 1324 when he, "knowing or in reckless disregard of the fact that an alien has come to, entered, or remains in the United States in violation of law, conceals, harbors, or shields from detection, or attempts to conceal, harbor, or shield from detection, such alien in any place, including any building or any means of transportation" or "encourages or induces an alien to come to, enter, or reside in the United States, knowing or in reckless disregard of the fact that such coming to, entry, or residence is or will be in violation of law." 

One means of committing that crime is tipping off a suspect about a raid.  Cases and headlines from around the globe reveal law enforcement officers charged with a crime for tipping off suspects about a potential raid. 

After his inauguration, President Trump apprised ICE to focus on raiding locations of especially dangerous illegal aliens.  Following Trump's orders, ICE began such raids over the last month.  That is when a Democrat legislator decided to take the law into her own hands and add lawless resistance to the so-called "resistance" groups aligned against President Trump enforcing the will of the voters who elected him president. 

Democrat legislator Michelle DuBois of Massachusetts posted the following on her Facebook page on March 27, 2017:

ICE raid in Brockton on 3/28 and 29th. If you get picked up by ICE call legal services direct line for immigration help: 774-488-5961. I got the following information from my friend in the Latin community: 'I have a message for the immigrant community of Brockton. Please be careful on Wednesday 29. ICE will be in Brockton on that day. If you are undocumented don't go out on the street. If there is a knock on the door of your house and you don't know who it is, don't open the door. I ask you to be careful.'

This opens the door to criminal prosecution on three fronts: first, tipping off suspects about the raid itself; second, advising suspects to take concealment actions that would avoid detection, such as "don't go out on the street" and "don't open the door," but "be careful" on the days of the raid, disclosing the likely methods of the raid in the process and enabling concealment for the purposes of continued illegal residency; and third, using her public office and public platform, with its implied access to inside information, to validate the raid's probability and the methods and means of evading it. 

Indeed, one of the priority areas of enforcement for the FBI's Public Corruption unit is "combating the threat of public corruption" in the area of immigration, especially due to the country's vulnerability to "drugs and weapons trafficking, alien smuggling, espionage, and terrorism," which such illegal entry and residency poses.

Boston needs no reminder of the risk of immigrant-inspired terror.  Given ICE's current focus of its raids on criminal aliens that pose a risk of safety to Americans, this tip-off wasn't for the gardener or the maid; it was for the dangerous criminal.  Ask Rockville parents about that risk.  Ask the friends and family of Kate Steinle.  Ask Trump State of the Union invitee Jamiel Shaw.  In their name, prosecute DuBois.