QUOTE:
a law like this imposed from the distant centre will likely be less effectual
I don't want to be trite about this (thinking how abortion clinics and doctors have been intimidated, even terrorised in America), but would effecting it be that difficult? Just tell Mart and Pete that it's in place, outside their area of authority, and any joint tantrum closing down Stormont will result in renewed direct rule.
Generally, I'm in favor of administrative devolution, legislative centralisation. If (notionally) Brussels can do a better job making laws than Belfast, leave them to it.