2 Answers

Yes. They must have a warrant in order to intrude. Unfortunately the Patriot act has all but killed the 4th amendment. Now if they even suggest you might be a terrorist, they can invade, arrest and detain without a warrant, without reading the Miranda rights or allowing you to seek legal counsel. 

Our rights to secure anything away from government knowledge has basically evaporated into thin air. When a cop comes to my front door I invite them in and offer whatever I can that may help. My door is always open to the police and if they are looking for anything in particular…drugs etc I tell them where it is what it is and where I got it. I hide nothing and don’t need to hide anything. That doesn’t mean I haven’t had things the police would look for but rather the most unsuspecting thing a person can do is welcome the police with open arms a smile. Act frightened, by police intrusion behave jittery and jumpy and you could get shot. Behave yourself and the police will generally leave you alone. Surviving a raid is less dramatic when you are openly friendly and cooperative. A cop hit me in the face during a street riot. I turned to him and said, “Thank you! I just wanted to know how to get out of this scene. I was directed down the street where I went. (Chicago anti-war  Riots in the 1960s).