This work presents a structural reinterpretation of magnetism as a constraint geometry governing the accessibility and routing of degrees of freedom. Rather than treating magnetic fields primarily as forces acting on charged particles, we propose that they function as geometric structures that restrict and organize admissible motion. Within this framework, magnetic fields reduce the dimensionality of accessible motion by constraining degrees of freedom perpendicular to field structure while permitting preferential routing along field-aligned pathways. Alignment, filamentary structure, and anisotropic transport are therefore understood as consequences of constrained accessibility rather than force-driven behavior. This perspective provides a unified explanation for a range of observed phenomena, including filament formation in molecular clouds, suppression or regulation of gravitational collapse, and directional energy transport in plasma systems. Collapse is interpreted as requiring accessible inward pathways; when magnetic constraint restricts these pathways, collapse is delayed or suppressed. Energy transport is similarly governed by constraint geometry, with energy flowing along admissible routes defined by magnetic structure. This connects directly to structural relaxation processes in which breakdown of coherent routing leads to energy accumulation and dissipation. The framework complements standard electromagnetic theory while shifting emphasis from force-based dynamics to constraint-based accessibility. Magnetism is therefore positioned as a primary regulator of physical behavior, shaping system evolution by determining which configurations and pathways are physically admissible.