What are the laws regarding having the keys in the ignition or not and being drunk?
For instance, if I walk out of a bar plastered and get in my car (in driver’s seat) and stick my keys in the ignition (but don’t turn my car on), then a cop sees me, is that considered drunk driving? Can I be arrested for that?
What if I walk to my car plastered from a bar and go sit in my car (in the drivier’s seat) and don’t put the keys in the ignition, then a cop sees me, can I get in trouble?
It depends on the state. They have to draw the line somewhere. I have heard about the keys in the ignition rule before. In fact, the police told me I got away with that type of thing before because of it but I don’t know how accurate that was in a legal sense. Again, I believe some states do use that standard and others use something else. Sitting in your passenger seat may be a good way to get away with it most places if you really want to sit in your car but don’t need to drive.
YES
Your are drunk, and in control of the car with keys in ignition. Engine running or not makes no nevermind.
Off to the drunk tank and a talk with the judge/magistrate.
NO
Of course this depends on the local jurisdiction where the offense occurs.
If you acknowledge that it depends on the local jurisdiction, how in the world can you possibly answer yes to the one and no to the other?
In some places, you will be charged with Care and Control while impaired. That carries a criminal code conviction in Canada, the equivalent of a felony in the USA.
To expand on GingerOfTheNorth’s point, to be charged with impaired driving you only need to have “care and control” of a motor vehicle while intoxicated. The vehicle does not have to be running, as long as you have the keys and are sitting in the driver’s seat. Sit in the back seat if you want to sleep.
Even if you get in the passenger side, or the back seat, you could still be charged with public drunk or something similar. The charge may or may not stick at trial, but it would get you off the street until you sober up.
In Ohio we have § 4511.194:
Unfortunately, I am well acquainted with this charge. 
That’ll learn ya to get in your trackless trolley with a load on.
All aboard !
In Washington state the law is called Being in actual physical control of a motor vehicle while under the influence.
I believe there are two reasons for these laws: 1)so that if you just stopped right before being contacted by the police, they don’t have to build a case to prove you were driving, and 2) if you’re in control of the vehicle, you easily could pull back into traffic, 3) Hi . . . (OK, I won’t do it).
IANAL but IIRC in some states, if the keys are in your pocket, and you’re sleeping it off in the back seat, you can still get a DUI. I think Illinois is one.
From your link:
They’re not defining “actual physical control”. Everything else just determines if they’re DUI or not.
I’ve often wondered how motor homes and travel vans factor into this, or the fellow who lives in a van down by the river w/ his family.
Saw a guy ride down the street on a bicycle and get a DUI. He was biking to avoid it but they got him anyway. Cops told me it was a legal arrest.
I’m sorry about that Crafter, but it is an improvement under the old law because it has less stiff penalties that the drunk driving statute itself Ohio R.C § 4511.191.
Before the physical control law was enacted a person was considered driving drunk even if he had pulled off the road to sleep it off if he still had the keys in the ignition. I know of one sad case where a guy, who was an alcoholic with previous DUI convictions was living with his mother in a tiny apartment, had an argument with his mother in the apartment on a hot summer night when the AC wasn’t working, went down to the sit in the car and listen to the car radio until his temper cooled off, and was charged with drunk driving. The cops came because someone complained about the noise from the car radio.
IANAL, but in my experience, in Las Vegas, you can be arrested if you’re in the front seat. Doesn’t matter if the car is on, if you have the keys on you, you can get busted.