Whitney Houston: Here's Proof Emmy Auction Is Illegal ... TV Academy Sues

Whitney Houston's Emmy award will NOT be auctioned off without a fight ... the Television Academy just filed a lawsuit accusing Heritage Auctions of theft.

TMZ broke the story ... the Academy is trying to block Heritage from putting the statuette on the block -- on behalf of Whitney's family -- claiming it contractually MUST be returned to the Academy.

In the docs -- filed in L.A. and obtained by TMZ -- the Academy included the sticker it says has been affixed to the bottom of EVERY Emmy handed out between 1978 to 1994. Whitney won hers in 1986.

The sticker makes it clear the statuette is the Academy's property and the winner's heirs are "obligated to return" it ... as opposed to selling it or throwing it away.