There's no question that shareholders of Wells Fargo (NYSE:WFC) have done well of late. Over the past year, shares in the mortgage giant are up nearly 18%. And if you go back two years, they're higher by an impressive 36%. But that performance is little consolation on days like today, when its shares are trading lower.

The impetus for Wells Fargo's lagging performance appears to be twofold. In the first case, as my colleague Robert Eberhard discussed yesterday, the New York Attorney General's office has announced that it may sue the bank, as well as Bank of America, for violating the multibillion-dollar National Foreclosure Settlement that the nation's five largest mortgage servicers entered into at the beginning of 2012. The AG has purportedly uncovered 339 violations of the accord between the two banks -- 129 attributable to B of A and 210 to Wells Fargo.

At this point, it's too early to say what the impact of a suit, if one is indeed filed, will be on either of these banks. On the one hand, there's speculation that the New York prosecutor may not have standing to file an independent case based on the language of the agreement itself -- in which New York was joined by 48 other states and the federal government. But on the other hand, if it is able to file such charges, the move could expose the lenders to additional liability that investors had likely assumed had been put in the rearview mirror.

Beyond these lawsuits, moreover, banking regulators are working to finalize a number of rules called for under the Dodd-Frank Act. Since JPMorgan Chase's London Whale scandal last year, there's been a growing chorus of support for higher capital requirements at the nation's largest banks. Two senators recently introduced legislation to this effect, the Federal Reserve governor in charge of regulation has proposed tighter liquidity requirements, and the Comptroller of the Currency Thomas Curry, one of the industry's primary regulators, said today that there's an active discussion underway about whether to make changes to leverage ratios. Suffice it to say, any one of these measures, let alone all three of them, would crimp the bottom-line at banks like Wells Fargo.

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