Despite the perception that they are “too big to jail,” Manhattan’s U.S. Attorney, Preet Bharara, is moving closer to filing criminal charges against two large financial institutions. According to The New York Times, the cases “could produce the first guilty plea from a major bank in more than two decades.”

Prosecutors have been regularly meeting with regulators over filing charges against Credit Suisse for providing tax shelters to Americans and against BNP Paribas, France’’s largest bank, for doing business with countries blacklisted by the U.S. such as Sudan and Iran.

The reason these likely impending criminal charges are so monumental is that banks are rarely indicted due to fears that doing so will have a negative impact on the economy. As Matthew Zeitlin explains at BuzzFeed, “It’s hard to indict a bank without killing it.” The fear is that a bank charged with criminal wrongdoing will have its charter revoked, essentially shutting it down.

Since the 2002 collapse of Enron and its accounting firm, Arthur Andersen, prosecutors have favored what are known as “deferred-prosecution agreements” which suspend charges against banks in exchange for concessions. Last December, for example, JPMorgan paid more than $2 billion in fines for its involvement with Bernie Madoff, but was mostly spared from admitting to any criminal wrongdoing. In 2012, HSBC entered into a deferred-prosecution agreement over money laundering charges and avoided criminal prosecution.

Bharara’s new strategy to pursue criminal penalties, however, is to coordinate with bank regulators about punishing banks without burying them. By gaining assurance that regulators won’t revoke a bank’s charter, prosecutors can pursue criminal penalties without fear of wrecking the financial system. That doesn't mean that proceedings don't require finesse, however. In the BNP case concerning money laundering, prosecutors are probably going to cite sanctions law violations instead of laundering, since laundering violations trigger automatic debarment.