The Situation Sues Over Alleged GTL Rip-Off ... TOLDJA SO!

The Situation's word is his bond -- weeks after the "Jersey Shore" star threatened to sue some guido-themed lifestyle company for ripping off his "GTL" trademark ... his lawyer filed a seething lawsuit to put the company out of business.

TMZ broke the story last weekend ... Sitch fired off a cease and desist letter to a website called MyGTLFuel.com -- which sells everything from energy shots to tanning lotion -- claiming they better quit exploiting his trademark ... or they'd face legal action.

Well, MyGTLFuel hasn't gone anywhere ... so Situation filed suit earlier this week -- asking a judge to force the site to cease all GTL-related operations and destroy any infringing merchandise.

Dana Valentino -- who owns GTL Fuel -- tells TMZ, The Situation has no case -- insisting the "Jersey" star has applied for the "GTL" trademark, but doesn't outright own it ... yet.