No the feds can not just enter and arrest. At least under Obama. That is the whole point that so many people are pissed off. Obama would not send in ICE or anyone else to do this because they need their votes and most importantly, their children votes. San Francisco just awarded a illegal $140,000 because the local law called ICE on a him after he was detained for a crime. They awarded him because it was against their sanctuary city law. Let me explain this. Not only is this guy illegal. He has enough empowerment to show up to a court of law in the freaking city and go to trial to sue for this and to collect his money without fear. Let that sink in.
Illegals protest in broad daylight in San Jose, CA wanted equal rights to citizens. Happens all the time. Can you imagine how empowered you must feel to not only live in a country but to actually decide to protest and disrupt flow of traffic as an illegal? They had zero worries that they would be detained or arrested by ICE.
Not only do they look the other way in case of illegal aliens but they encourage it all the way from the mayor of San Jose to the president Obama.