What did rousseau mean when he stated that if any individual wants to pursue his own self interests a the expense of the common good, "he will be forced to be free"?

The quote you are speaking of comes from Book 1, Section 7 of the Social Contract.

"This means nothing less than that he will be forced to be free; for this is the condition which, by giving each citizen to his country, secures him against all personal dependence

Explanation:Here are some definitions to help you understand better what the quote is trying to say.

The sovereign: The sovereign serves as the active role of a state or country. It operates in the best interests of the people it serves. The sovereign cannot do anything to break the Social Contract, for this would cause the self destruction of sovereign itself.

Subject: subjects submit themselves unconditionally to social contract. Within this contract, individuals cannot hold any rights that would stand in opposition to the state. Since all people are unconditionally bound to social contract, no ones loses their freedom.

In being unconditionally bound to the social contract, all individuals retain their freedom. When a subject attempts to break the social contract, the majority will force the individual to abide by the social contract in the form of laws. Since breaking the social contract would result in loss of freedom of the individual, he will "be forced to be free" or to be forced retain his freedom within the terms set by Social Contract.

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