If an officer sees illegal activity or contraband in plain view, they can act without a warrant. A warrantless arrest is usually a "strike while the iron is hot" situation.Law enforcement officials can also search a residence, person, or electronic device with the consent of the person or owner without a warrant. When can law enforcement arrest me without a warrant? Arrest without a warrant means taking someone into custody without a written order from a judge. Ignoring a warrant in California has consequences, including a charge of 'Failure to Appear. When can law enforcement arrest me without a warrant? Criminal Law: When Are Warrantless Searches Allowed in California? Knock and notice means that before entering a dwelling to make an arrest, with or without a warrant, officers must give notice to the person inside. What is an Arrest Warrant?