Regulations  
Yes, Virginia, plain language regulations do exist.

American Bar Association resolution–ABA urges the federal government to write regulations in plain language.

The Office of the Federal Register supports plain language. See their
Document Drafting Handbook (DDH)
Plain Language Tools
Making Regulations Readable
Drafting Legal Documents

The Register even shows you how to rewrite an existing rule in plain language in Rewriting a Short Rule: Step by Step.

From Plain Language.gov
Lessons in Drafting from the New Federal Rules of Civil Procedure (Parts 1 - 5) by Joseph Kimble. Michigan Bar Journal 2007 offers some drafting tips and examples from the new FRCP rules including formatting, consistency, outdated and repetitious material.
Kimble –
Lessons in Drafting from the New Federal Rules of Civil Procedure (Part 1)
Lessons in Drafting from the New Federal Rules of Civil Procedure (Part 2)
Lessons in Drafting from the New Federal Rules of Civil Procedure (Part 3)
Lessons in Drafting from the New Federal Rules of Civil Procedure (Part 4)
Lessons in Drafting from the New Federal Rules of Civil Procedure (Part 5)