police and law enforcement
(Answer is applicable to the USA only): A warrantless arrest is never served. A warrantless arrest is performed. Following the warrantless arrest, the arresting individual (typically) or authority is required (usually) to provide the courts with a warrantless arrest affidavit wherein the person making the arrest articulates the probable cause for the arrest, which then is submitted to a judge for review. The arrested person will already be in jail or otherwise in custody (and possibly even bonded out), before the signed warrantless arrest affidavit becomes available to the arrested person.
According to John Yoo, a warrantless search or seizure is reasonable if it is based on the President's inherent constitutional authority during times of war or national emergency. Yoo argued that the Fourth Amendment does not apply in these circumstances, allowing for warrantless actions in order to protect national security.
in your presence the person is actually committing, about to commit a felony
Incident to an arrest
The government's interests outweigh all other concerns APEX
true
Conduct a warrantless search and seizure.
warrant
In the manner of the way the actual arrest goes down, very little. The one major difference between arresting for a felony versus arresting for a misdemeanor, is that for a warrantless arrest of a misdemeanant the officer must have atually witnessed the misdmeanor offense take place in order to make the arrest. The only exception to this would be (in jurisdictions that have such offenses) there are certain so-called "Probable Cause Misdemeanors" for which an arrest can be made even if the officer didn't observe them take place.
The court allows the government to conduct a warrant-less search and seizure.
In order to make a warrantless arrest, a police officer must be given permission to enter or be in an emergency situation. In both instances, the officer must have sufficient probable cause to make the arrest.