When Does Selective Interaction Suppression Support a Physical Transition-Law Claim? Falsifiability, Subsystem Identity, and Mechanism Identifiability

This theoretical/methodological physics preprint studies the inference problem that arises when selective suppression of interactions between a designated subsystem and its exterior is interpreted as a candidate physical transition. The work separates formal selective suppression, falsifiability of a specified response subclass, physical instantiation at the claimed interaction scope, and mechanism discrimination against registered alternatives. It derives (i) an operator-norm upper bound on contamination caused by subsystem-identification error and (ii) a selector-law-free rank-one constraint for a fixed-map common-scalar response subclass. A restricted two-sector model and an ordinary variable-coupler countermodel delimit what response measurements can establish. The work does not establish a physical transition law for a real body, does not establish D_real, and makes no attribution to V0.