As a union member, part of a collective barganing agreement, Am I bound to pay into the Union Medical Plan even though I do not use the insurance because my wife's coverage is better? I am currently paying 120.00 per week for medical insurance I do not use, this is in addition to the monies my empolyer puts in for me. My wife works at a hospital and has better insurance than I do. I want to opt out of my plan but they tell me I still need to pay into the plan out of my pocket.

First this is not a "law" but your union rules, so you need to talk to your shop steward or union office and ask them what the rules are.
Often this is the case.

In most cases you are a member of a collective bargaining unit and all members get the same benefits and cost. It's a package deal not ala carte, take all or none. Talk to your steward but this is the case for most bargaining groups.