This is the kind of thread that will generate tons of useless "get a new boss" posts. I hereby declare that I will -- any such posts unless they provide a creative way of getting rid of the current boss :) (Special rules: No voltages in excess of 220V, no items considered "military-grade weapons" in the respective country)

Seriously though, I think this comes from one of three things:

1. Micro-managing boss that doesn't know enough I can't think of anything to do here.
2. Acceptable boss who has a wrong idea In this case it's merely a matter of gathering enough evidence to support your position. Any ideas of what form such evidence would take?
3. Actual portability concerns Some modules are built on C code that _isn't_ portable. So either you need to prove that your module IS portable, or concede defeat.

In general, if you can get the boss to explicitly define why "No", you can try to prove "Yes". Bosses, however, don't often like to have their judgement questioned, so some delicacy is required.