The problem of determining intended meaning is a key topic in the study of linguistic processes. This paper is part of a research that attempts to answer the question: how do agents involved in a linguistic controversy determine the intended meaning of a sentence? The main thesis of the research is that the determination of meaning is driven by agents situational interests. The process is analyzed in two phases (individual and contractual), and the thesis is respectively declined in two hypotheses. Here I analyze the first phase. The hypothesis is that an agents situational interest drives the individual choice of meaning for ambiguous sentences. It is argued in particular that formal semantics, the dictionary, context of use and domain knowledge are not sufficiently powerful to determine a unique meaning (condition of legitimacy). From this it follows that an agent can legitimately choose a meaning (i.e. make a decision) given a set of contextually admissible interpretations. This proposal should impact on the problem of meaning under determination. The contribute consists in providing a further tool to determine how agents assign meaning to sentences of natural language. Finally, I shall sketch out a semantic function which its input is a set of contextually admissible interpretations and agents situational interest, and its output is a ranking of ordering of interpretations. The approach is theoretical, but the research is based on cases of disputes concerning ambiguous clauses in employment contracts.