[PaulDavisThe1st]

I suspect because "make a law" conveys some sense of the actual process of legislating, whereas "just pass a law" sounds as if it deliberately minimizes the process and makes it sound as if it is something trivial to do.

[trutannus]

I thought it was a fair summary, but I can also see how someone would arrive at your conclusion. I read it as minimizing, but you make a fair point.