When Bank of America (BAC) agreed to buy Countrywide, it didn’t just take on a mountain of questionably valued mortgage-related assets. It also took on huge legal liability.

San Diego City Attorney Mike Aguirre, who has a penchant for punitive lawsuits that rarely result in much more than a media frenzy, is accusing Countrywide of defrauding thousands of San Diego homeowners. A lawsuit has already been brought at the state level by California Attorney General Jerry Brown, as well as in several other states, including Washington and Illinois.

San Diego's suit takes aim at Countrywide’s alleged practice of coercing borrowers into risky adjustable rate mortgages (ARMs). Aguirre hopes to make San Diego a “foreclosure sanctuary” by preventing foreclosure proceedings on any property secured by a subprime ARM where the borrower owes more than the home is worth. (For more on what the glut of upside-down homeowners means for the future of the housing market, please read Finding the Bottom in Housing.)

The litigious City Attorney isn’t satisfied with just taking aim at Countrywide (and, by extension, Bank of America). Aguirre said he’s planning similar suits against Washington Mutual (WM), Wells Fargo (WFC) and Wachovia (WB).

While Aguirre’s heart may be in the right place, foreclosure moratoriums aren’t part of the road to recovery for the housing market. Opportunistic mortgage market participants are buying delinquent mortgages on the cheap, forgiving some part of the debt and giving borrowers a fresh start. Government intervention in this process will simply scare off lenders, since they'll have limited recourse if the loan goes sour.

At best, such suits will simply drive up the cost of new mortgages. At worst, they'll bring the recovery process to a standstill.

Foreclosures are nasty, painful and tragic. They are, however, a necessary part of the mortgage process, enabling lenders to recoup losses on bad loans.

Mandating an end to foreclosures is like telling the IRS it can’t go after tax evaders or preventing cops from chasing down burglars. This is not to say victims of foreclosures are criminals or necessarily deserve to be thrown out on the street, but living in a law-abiding society means that contracts must be enforced.

The moment we waive one group’s obligation to honor their collective word, the floodgates are open.

This certainly isn't the last lawsuit we’ll see following the collapse of the mortgage market. In fact, it’s just the tip of the iceberg. A couple years from now, when Option ARMs begin to reset, class action lawsuits will bear down on lenders like a rumbling avalanche rolling down a steep slope.

Banks would be wise to get long some lawyers.