@Blickers,
Yeah, I agree with you and the other posters here.
Courts don't rely on the DI as "law" but in the course of stating the rationale for giving their opinions, I think they have often cited it for the ideas and ideals it contains.
Courts often look to the "legislative history" (premlinary drafts, debates on the floor, etc.) of a law in an attempt to ascertain the true intention of the statute. It helps them properly "interpret" the statute in question. The DI is it's own kind of "legislative history," which preceded the drafting of the constitution.