Generally speaking, business and organizations--including non-profit clubs--are bound by the agreements they sign, including non-competition agreements. Therefore, from what you write, it would seem that the vendor could enforce the agreement against you. However, that is just a general answer; for a specific answer, you need to consult with an attorney who can evaluate the precise language of the agreement and situation for you. For example, various types of non-competition agreements are often "blue penciled" by courts to make them less restrictive (e.g. apply for a shorter period of time) if it is the case that the agreement is too far-reaching. Also, if there was some breach by the vendor, some misrepresentation by them during the negotiation of the agreement, and/or some confusion between the two parties as to what was being agreed too, that may suffice to provide grounds to void or at least modify the agreement. It is therefore worthwhile to consult with an attorney, to see what your rights and recourse may be.