[lproven]

> you can't legally force vendors to open source the drivers they distribute

You can't, no, but that is looking at the wrong end of the problem.

What you can do is say, "we are the government of $X and we buy $Y billion of $currency of equipment per year, every year, and we will only buy from vendors who make all their drivers and firmware FOSS."

Then vendors will fall over one another in their haste to get a slice of that pie.

This is how we got desktop power management: the US Gov't Energy Star initiative.

This is why A/UX happened and how Apple got into UNIX: the US Army required POSIX as a condition of purchase.

Result, indirectly: OS X.