It is impossible to speak knowledgeably about the embedded nature of law in society without addressing the central notions of Karl Marx’s political theory
It means that "law is ingrained within society", ie. rules and regulations, formal or informal, would naturally develop within a community of people.
The best restatement I can come up with for it is "the fact that law is woven into society's guts". If this is too metaphorical to be clear, let me know and I'll generate another.