Stuart Brunton was snared as he turned up for the Jambos semi final clash with Inverness Caledonian Thistle last Saturday.
The 21 year-old, of Gracemount, Edinburgh, was held after a smoke canister fell out his pocket after going through the turnstiles.
It lead to Brunton appearing at Glasgow Sheriff Court.
He pled guilty to a charge of possessing a controlled substance which emits smoke.
Brunton will be sentenced next month.
But, Sheriff Allan Findlay meantime banned him from entering a football stadium within the UK.
It means Brunton will not be back at Hampden for the Hearts and Celtic final on May 25.