arXiv:2605.01558v3 Announce Type: replace-cross Abstract: Ensemble control specifies probability laws on admissible trajectories, including their temporal dependence. Starting from an arbitrary closed behavior, we organize its laws into a framework that connects standard probability-measure geometry, occupation-measure control, and data-driven trajectory parametrization. Classical convexity and extreme-point properties describe the feasible laws, while classical Bellman duality governs additive control objectives. On compact state and input spaces, full-path constrained duality for continuous trajectory functions gives primal attainment and zero gap whenever feasible. For controllable linear time-invariant systems, the noise-free Fundamental Lemma yields an equivalent law-level Hankel factorization, with a canonical pseudoinverse lift. The factorization transfers trajectory-law constraints exactly to coefficient space and connects them to covariance control. Explicit noisy-Hankel bounds quantify subspace approximation for second-moment-bounded laws under known rank and Gaussian output measurement noise. Numerical studies include a nonlinear reset problem whose nonadjacent correlation constraint requires temporal memory, covariance-constrained optimization, and noisy-data policy evaluation. Known transition kernels provide a further structural perspective through history-conditional consistency.