If you live in Tennessee, July 1st 2011 could become a day that lives in infamy for anyone caught sharing login info with pals to access streaming media. That’s D-Day for a bill just passed by the state that criminalizes using a friend’s login—with or without permission—to stream movies or songs via services like Netflix and Rhapsody.

The law goes into effect July 1st and makes stealing $500 or less a misdemeanor punishable by up to a year in jail and a fine of $2,500. Slip past the $500 threshold in purloined media and it’s an automatic felony, which means serious jail time and much heavier fines.

The bill, supported by the recording industry, seeks primarily to penalize hackers and illegal music traffickers, but it’ll also be wieldable as a way to go after anyone who’s sharing streaming subscription login info with members outside their household. It’s basically the old “you can’t share cable TV” idea expanded to encompass “entertainment subscription service.”

“What becomes not legal is if you send your username and password to all your friends so they can get free subscriptions,” said Rep. Gerald McCormick, the bill’s House sponsor, per The Tennessean.

Okay, so some of that’s just common sense, right? Do you share subscription login info with more than family? With your football teammates? Your entire college dormitory cohort? Maybe not the smartest move. That info’s tagged to Internet Protocol (IP) data, which indicates where each user’s logging on from, making it a snap for companies like Netflix or Rhapsody to determine if someone’s routinely using login info from multiple locations.

But wait, you’re allowed to login from places other than your home, aren’t you? I do with my iPhone, and can’t I sign into a friend’s PS3 and use my Netflix ID to watch movies at their house? Maybe yes, maybe no—it depends on each service’s terms. According to Netflix’s FAQ, what you can do depends on your membership plan:

If you are on the Watch Instantly Unlimited plan or the 1-disc-out-at-a-time plan, you may watch only one device at a time. If you are on the 2-discs-out-at-a-time plan, you may watch on up to two devices at a time. Members on the 3-disc plan can watch on up to three devices. The maximum is four devices — available for members on the 4-or-greater-discs-out-at-a-time plan.

Under Netflix’s terms, you have “up to six unique authorized devices activated…at any given time.” Netflix’s usage stipulations define latitude as a “members of your immediate household,” though they neglect to define what “household” means. Blood relatives? Adopted family members? Friends sleeping over? You staying at a friend’s house for the weekend? When I visited a distant friend in February, I took my PS3 along so we could stream Netflix movies through his Internet service provider. Legal or illegal? Legal, I’m fairly certain, but you can see where this gets weird as everything becomes massively distributed.

According to Bill Ramsey, a Nashville entertainment lawyer, the law probably won’t be used to target people under the same roof, in part because small violations aren’t easily detected. But “when you start going north of 10 people, a prosecutor might look and say, ‘Hey, you knew it was stealing’,” Ramsey told The Tennessean.