"Laid down" is the past tense and past participle of "lay down". It means you put something on a surface or established rules, terms, or principles. In casual speech, some use it to mean someone reclined to rest.
If the crowns of all the kingdoms of the empire were laid down at my feet in exchange for my books and my love of reading I would spurn them all. François Fénelon
The laws of physics is the canvas God laid down on which to paint his masterpiece. Dan Brown
Do you know what morals are? Morals are an obedience to rules that people laid down to help you live among them. Theodore Sturgeon
It may be laid down as a primary position, and the basis of our system, that every Citizen who enjoys the protection of a Free Government, owes not only a proportion of his property, but even of his personal services to the defense of it. George Washington
Common sense is actually nothing more than a deposit of prejudices laid down in the mind prior to the age of eighteen. Albert Einstein
Submit to the rule you have yourself laid down. Latin Proverb