For lex mercatoria material on party autonomy or freedom of contract:
http://tldb.uni-koeln.de/TLDB.html
Click TLDB's "List of Lex Mercatoria Principles".
"The parties are free to enter into contracts and to determine their contents (principle of party autonomy."
The TLDB database provides annotations to this text. The TLDB annotations address Doctrine, Principles/Model Laws, Conventions, National Legislation.
Pace Law School
Institute of International Commercial Law - Last updated January 28, 2003