You might think that Samsung stopped paying Android patent licensing fees to Microsoft because of concerns about the viability of Microsoft's Android patents , but that's not what Samsung has been arguing. Instead, Samsung's position has been that Microsoft's Nokia acquisition breached the patent license agreement.

Now, Samsung has added some more details to this defense: Paying Microsoft after the acquisition would have lead to antitrust violations.

This move came as no surprise to lawyers who've been following the case. One intellectual property (IP) attorney whose firm is covering the case closely said that Samsung is simply adding another argument to their contention that their existing Microsoft Android patent deal is invalid on business contract grounds.

According to Reuters, Samsung said it agreed to pay Microsoft Android patent license royalties in 2011, but the deal also stated that Samsung would develop Windows phones and share confidential business information with Microsoft. If Samsung were to sell a certain number of Windows phones, then Microsoft would reduce the Android royalty payments.

That, of course, didn't happen. Windows Phone's already small marketshare has actually declined since 2013. Samsung, the leading Android phone vendor, has only one Windows Phone line: the Samsung ATVI S.

Further, Samsung argued that since Microsoft acquired Nokia, it's become a Samsung hardware competitor. This meant that Samsung could no longer share sensitive information without running afoul of US antitrust laws. In the filing, Samsung said: "The agreements, now between competitors, invite charges of collusion."

In a statement, according to Reuters, Microsoft denied Samsung's claims. Microsoft stated that they remained "confident that our case is strong."

Samsung paid over a billion dollars in 2013 alone to Microsoft for its patent licenses on sales of not quite 300-million phones. That's enough money to make anyone consider going to court if they think they have a case.

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