FBR Capital Markets said Visa Inc. (NYSE: V) and MasterCard Inc. (NYSE: MA) have been volatile for over a year due to the Durbin Debit Interchange Amendment. The brokerage said it is worth watching in the next few months in the wake of final regulations expected from the Federal Reserve.

"From our perspective, the most important aspect of the final regulations will be how the Fed rules on network exclusivity. We highlight some of the key events over the next several months, providing analysis on what we believe are the most likely scenarios, and highlight the volatility for both Visa and MasterCard following previous actions related to the Durbin amendment," said Edward Mills, an analyst at FBR Capital Markets.

Mills said the Federal Reserve missed its April 21 deadline on the final rule for what is a "reasonable and proportional" interchange fee, but a decision is anticipated this month with implementation by July 21. It remains unclear if this part of the rule will also include a final ruling on network exclusivity

Mills believes the most important part of the rule for Visa and MasterCard is network exclusivity.

Consensus is building around Alternative A (elimination of PIN exclusivity), but lack of confirmation still has Mills concerned that Alternative B (elimination of PIN and signature exclusivity) has an outside chance of making its way into the final rule. This rule is not due until July 21. Visa and MasterCard could react negatively should the Fed adopt Alternative B or even delay ruling on the issue until July.

Mills continues to believe that Senator Tester is short of the 60 votes to get the legislation passed. The bigger battle may be finding a way to even get a vote. This calculation could change if the final rule is delayed beyond the next few weeks and delay-supporters argue that there is not enough time to implement the rule by July 21.

On Visa's second quarter earnings conference call, management disclosed its plans to announce Visa's global mobile e-commerce strategy this week. Given the increased investor focus on mobile strategies, Mills expects shares of Visa to react positively to the announcement.

Based on historical volatility surrounding interchange-related announcements, Mills expects increased volatility around the Fed's announcement regarding the final debit interchange regulation.

"Currently, it does not appear that the options market is pricing in a significant amount of volatility through June expiration. We note the potential for additional volatility following the release of the final rule, the mobile e-commerce strategy by Visa, or any clarity related to legislation to delay final implementation," said Mills.

Visa stock is trading down 0.42 percent at $79.08 while MasterCard is trading up 0.29 percent at $275.05 on the NYSE at 9:44 am EDT.