This applies specifically to California loans, though I'm sure there are similar civil codes in other states.
Wow.....I actually like this liberal policy!! YIPPEE!!! 
OK, back to reality.....seriously.....I believe that this can help plenty of distressed homeowners....not the ninnies who are whining about their increase......or the ones who took cash out once a year for 5 years straight, but the ones that are TRULY faced with a rate increase that they cannot handle......
California Civil Code 1916.5.5
(5) The borrower is permitted to prepay the loan in whole or in
part without a prepayment charge within 90 days of notification of
any increase in the rate of interest.
Simple but true.....if you are a homeowner in need of assistance, a lender who may have the deal figured out but cannot get around the prepayment penalty, or a realtor who is looking to help a challenged seller, consider this often overlooked part of the civil code.
You will be glad you did......figure that for most clients if they have a $2K monthly payment, and the standard prepayment penalty is roughly six months worth of interest payments, you're looking at a savings of $12K that would otherwise go to the bank, or you could be taxed on in a short sale situation if you fail to make arrangements.
Feel free to touch base if you need additional guidance! Have fun with a fellow friend, lender, or realtor, and see the deer in the headlights look when you mention that you can do this.........

Bill - Looking forward to Friday. Like the tag! That is a "window" many people do not know about.