Being a party to an event, agreement, or decision implies being involved in it. The antonyms for this expression would be "not involved," "unconcerned," "disinterested," "non-participating," "uninvolved," and "detached." These antonyms describe a state of being neutral, indifferent, or aloof in regards to a particular matter. In some cases, being a party to something can have negative consequences or implications, and opting to not participate or be involved can be a wise decision. However, in other situations, being a party to something can be necessary for progress, growth, or change. Ultimately, the choice to be a party to something or not depends on individual circumstances and personal values.