At the 1991 IBT Convention, Teamsters won the right to vote on all supplements and riders to the national contract. Prior to that time, there were no votes on regional supplements, which means that a Teamster in California could vote to ratify a supplement in New Jersey, and vice versa. Employers with national contracts used it to divide and conquer Teamsters members.

How did we win this right? It's important to know, because if you know Teamster history, you can shape the Teamster future.
In 1990-91, members had the Right to Vote for convention delegates and for IBT President and International officers for the first time. Teamsters for a Democratic Union (TDU) helped Teamsters take full advantage of these hard-won rights.

We mobilized support for changing the constitution. We helped elect delegates committed to change.

One officer led the charge on the right to vote on supplements: Tom Griffith, the president of Harrisburg Local 776. Griffith worked with TDU on the wording of the amendment. Then he built support from other Pennsylvania locals. He got the President of the Pennsylvania Conference, John Morris, to introduce the motion. During 1990-91, TDU built up membership support for the change and TDU and reform delegates were prepared, and lined up at all the various convention microphones.
http://www.tdu.org/how_we_won_the_ri..._history_video