  Unitary operators are employed to investigate the violation of the Bell-CHSH
inequality. The ensuing modifications affecting both classical and quantum
bounds are elucidated. The relevance of a particular class of unitary operators
whose expectation values are real is pointed out. For these operators, the
classical and quantum bounds remain unaltered, being given, respectively, by
$2$ and $2\sqrt{2}$. As an example, the Weyl unitary operators for a real
scalar field in relativistic Quantum Field Theory are discussed.
