Once Congress reconvenes next week, the NDAA bill will be sent to a formal House-Senate conference committee to resolve all the differences. There is a strong norm in Congress, backed by rules of each chamber, that if both the House and Senate versions of a bill contain identical provisions, that provision must be left intact in the final conference agreement. This usually means that if the House and Senate bills both have provisions that are not quite identical, but are very very very similar, then the conference is supposed to end with some sort of difference-splitting germane modification of the provisions.

On this issue in particular, not only did the chairmen of the House and Senate Armed Services Committees consent to include the provision in their bill, but it was drafted by the bipartisan leaders of the Senate authorizing committee with mass transit jurisdiction (Banking). And the House provision has the support of that authorizing chairman, Transportation and Infrastructure’s Peter DeFazio (D-OR). The easiest way to derail a provision in conference is by some other committee asserting jurisdiction and killing it, but since the committees of jurisdiction don’t seem likely to do that, enactment of some version of the ban seems certain.

The White House weighing in in favor of the ban that applies to both buses and rail cars would seem to tip the scales even further towards the Senate version of the provision, but what makes this even more interesting is that the chief Congressional advocate for exempting buses from the ban is one of President Trump’s top allies in Congress, House Republican Leader Kevin McCarthy (R-CA), in whose district BYD’s 450,000-square-foot bus assembly facility is located.