What was the problem is that the guy seemed to think that laws didn't apply to him, starting with the fake license plate that likely indicated to the responding officer that this guy was going to be trouble.
The law is really clear that if you are operating a motor vehicle on a public street, you have to provide identification and the car must be registered.
Arguing with the cops about those most basic facts is rarely going to end well. On top of that, reaching for a clearly visible gun, without telling the police what you're doing can be fatal. As it was in this case.
Fake passport, too.
Several Police officers have been killed by Sovereign Stupids.