In this brief essay, prepared as part of a symposium on The New Federalism: Plural Governance in a Decentered World, I explore the regulatory dynamics at work: (1) in the operation of Securities Exchange Act Rule 14a-8, (2) in the interventions of then-Attorney General Eliot Spitzer in the national securities markets, and (3) in recent steps by the Securities and Exchange Commission to reconcile U.S. and international accounting standards. In each case, a distinct dynamic of regulatory interaction - what I term intersystemic governance - can be observed. In such cases, overlapping jurisdiction combines with various sources of interdependence to produce a regulatory scheme that goes beyond regulatory cooperation supporting each jurisdiction's pursuit of its own goals. Rather, it may produce something akin to joint, or intertwined, regulation of relevant individuals, institutions, or subject-matter. In such regimes, discrete sets of regulatory rules may collapse into a collective whole.