Orin Kerr has a blog post about the origins of what some may incorrectly view as a recent attack on Fourth Amendment protections – the ability of law enforcement to search you if they arrest you:
The search incident to arrest doctrine predates the War on Drugs, actually. In People v. Chiagles, 237 N.Y. 193 (1923), Benjamin Cardozo explained that the exception existed in ancient English common law and had continued to the present.
Read more of the history of the exception on The Volokh Conspiracy.
Although well-established in law, the topic is still a timely one for those who question the government’s ability to search a cell phone found on your person at the time of arrest and whether having a password on your cell phone would make a difference.