History of WWE’s “no compete” clause?

Are the WWE's "no compete" clauses in contracts relatively new, or have they always been around?  It seems like in the early years of the Monday Night Wars talent jumped from the WWF/E to WCW with little to no delay;  I.E.-Lex Luger, Madusa, Hall and Nash, etc.  

Luger and Madusa were special cases because they had been working without a contract.  Hall and Nash were at the end of their contracts.

A non-compete only applies while you're under contract.  Once the contract expires, you're free to go wherever you want the moment the contract is done.  The entire purpose of the non-compete is to prevent someone from quitting early and switching sides.  And yeah, they've been around FOREVER.  Since the 80s, in fact.