When its time to go to Brooklyn for the "meeting" with Barzini, Tom suddenly tells Tessio he can't go (either.)
Then, Willie Cicci emerges and grabs Tessio's gun.

My question is, was Tessio planning on doing the hit himself, if he was strapped with a gun? Or was this dramatic license?

Since Tessio, couldn't hang his hat in Brookly, I suspect he might have carried a gun for protection.

I think he just had a gun because he was a mafioso capo and carried it for protection. They were going to meet with Barzini's men, so it could have reasonably be assumed he had it on him "just in case".

I doubt he was going to do the hit himself; it probably would have been Barzini's men burst in and gun Michael down, Tessio pretends to shoot them (So any witnesses could point out to the Corleones that Tessio wasn't in on it).

I think Tessio was being set up himself, anyways. Even if Michael didn't know about it being a trick, I think Barzini's guys would have "accidentally" gunned Tessio down too, since Barzini's not stupid - Tessio would still be a traitor, and a traitor can't be trusted.

Although Cicci was wise to pat Tess down as a precaution, Mafia caporegimes seldom carry because they're obvious targets for law enforcement, and if they're caught carrying, they go right to prison without The Law having to prove anything else. So, they usually don't carry--but travel with bodyguards who do.

I think Barzini also would have had Clemenza killed at the same time. He'd have kept Tess on for a while to organize the remnants of the Corleones. But once a traitor, always a candidate for being whacked.

Why couldn't Tessio hand his hat in Brooklyn...I thought the meeting was on "Tessio's ground".

Perhaps the quote was meant to illustrate how much the Corleone's territory had been squeezed. Sure there was a little territory left, but not much.

I think that's just an overdramatic statement Tessio made. No doubt that the Barzinis and Tattaglias were looking to expand on Corleone territory, but you don't just walk in and take over territory from New York's biggest family. That only happens during a conflict or by negotiation.

Remember that Tessio makes the "hat" statement in the last meeting in Vito's office and that Clemenza also chimes in that in six months there won't be anything left to build on. I agree with TB though that Tessio normally wouldn't carry a gun, but that day was different because of the meeting. In any case, Barzini's people would take care of Mike.