Often, the legal system (and/or its functionaries) serves as a barrier to any proper resolution of the questions surrounding the narrative and plot structure.
The trees can serve as shelter from the rain. The organization serves as a model of social responsibility. The accident serves as [= is] a reminder of the dangers of drunk driving. Let that serve as [= be] a lesson to you.
"The lake serves recreation "; "The President's wisdom has served the country well"; "Art serves commerce "; "Their interests are served" Provide (usually but not necessarily food)
Someone who serves customers in a store or a bar helps them and provides them with what they want to buy. They wouldn't serve me in any bars because I looked too young.