Microsoft's forthcoming Lumia 950 and 950 XL phones are going to have rather limited promotion and availability in the US. The Lumia 950 will be available from AT&T, and both handsets will be available unlocked (and full price) from Microsoft directly. While easy access to unlocked phones is to be applauded, there is a lingering problem. The spec sheets of the phones indicate that they'll support the frequencies needed for AT&T and T-Mobile (though it's not clear if Wi-Fi calling will be supported), but they seemingly lack the CDMA and EVDO support necessary to make them usable on the networks of Verizon and, for those who care, Sprint.

This is unfortunate. While losing out on carrier promotion is obviously going to limit the impact that a phone can have, that might not be so terrible if at least customers who were interested in a platform could pick up an unlocked phone instead. Excluding support for the largest phone network in the US means that even this isn't an option.

What makes this confounding is that the handsets are believed to contain universal modems that support all the phone technologies in use in the US: both the GSM family, used by AT&T and T-Mobile (2G GSM and EDGE, 3G UMTS/HSPA/WCDMA) and the CDMA family (2G CDMA, 3G 1x/EV-DO), as well of course as the universal LTE. Microsoft would still have to make sure the antennas supported all the right frequencies and get the right FCC certification, but there's no real impediment to making a universal phone. Recent iPhones and several Nexus-branded devices have all had this kind of universality. The belief is that Microsoft has the right modem hardware, but for whatever reason decided to disable the CDMA portion.

It feels like Microsoft has dropped the ball, but last week the suggestion was made that it is, in fact, Verizon's fault: that Microsoft disabled CDMA support because Verizon would refuse to activate the phones on its network. As such, disabling CDMA simply avoids confusion and the frustration that would come of buying a phone that ought to work with a Verizon SIM, only to have the carrier refuse to allow its use. This was first claimed by Paul Thurrott on the Windows Weekly podcast.

It's tempting to paint Verizon as the bad guy. The carrier's support for Windows Phone has been lackluster, and the relationship between Microsoft and Verizon doesn't appear to be at all healthy. Microsoft isn't blameless here either. The KIN debacle in 2010 gave Verizon little reason to support Microsoft's future phone efforts, but Verizon, for its part, has not provided timely access to firmware updates, even when the carrier was given exclusives on compelling phones such as the Lumia Icon. In this light, claims that Verizon would refuse to activate the 950 and 950 XL feel plausible.

The problem is Verizon can't really do that. As one of the conditions for being able to operate in the 700MHz frequency band, Verizon's network (or at least parts of it) are subject to open access requirements. In short, any phone that's compatible and FCC certified must be authenticated by Verizon. There are constraints here; unlike the Carterfone decision in 1968 that opened up AT&T's wired phone network to any device that was safe and compatible, Verizon can, and does, still require that phones pass through a certification process before allowing them on the network. But that authentication process, conducted not by Verizon itself but by third-party testing services, is open to anyone willing to pay the fee. It takes a few weeks, but once a phone passes the tests, Verizon has no option but to authenticate.

We've seen this situation play out before. The Nexus 7 tablet had LTE compatible with Verizon's network, and the carrier initially presented roadblocks to owners of the tablet who wanted to activate it on its network. But these roadblocks seem to have been temporary. Although there were issues with the certification process—Google asked for testing to be suspended after it found a bug—unlocked Nexus 7s were eventually activated and successfully used on the Verizon network.

This is not to say that Verizon's certification process isn't annoying or an attempt to erect hurdles to make it harder to use unlocked phones on its network. The GSM carriers have no such constraint; simply drop one of their SIMs into a compatible phone and it'll spring into life immediately. If AT&T and T-Mobile can make their networks sufficiently robust that any device will work on them without any testing above and beyond what the FCC requires, it's not clear why Verizon can't do the same.

Ultimately, however, there is a process that Microsoft could follow to make the 950 and 950 XL compatible with Verizon's network. It'd cost some money for certifications, but so do many other things in the world of building mobile phones. That Microsoft is apparently unable or unwilling to enable CDMA and go through certification is a strange decision, and it's a decision that will limit the appeal and value of the 950 and 950 XL. But it's Microsoft's decision; not Verizon's.