All they have to do is make an anonymous phone call.
Today in Sanctuary Calif where public safety is not priority much like in congress.
Who is the next Kate Steinle going to be?
In law enforcement it is called “exchange of info.” If your agency prevents you from enforcing some law, you call for assistance from someone who can. LAPD was prohibited from impounding cars driven by unlicensed illegal aliens, so they would simply call for exchange of info to get an officer from another agency who could.
Just my opinion, but I think if some judge finds out that an “anonymous” source is found out to be a police officer, that said judge would throw out all charges and order the illegal alien be brought back into the US because “his” rights were violated. Pretty sad times.