Constitutionalists are nervous about preempting the entire field. In tort law, plaintiffs' lawyers trawl the country in search of a hospitable jurisdiction, and the craziest jury in Beaumont or Texarkana gets to determine the legal regime for the rest of the country. However, uniformity is preferable to diversity and choice only so long as the choices are being made by one's enemies. We have fifty different regimes governing corporate chartering. The reason is that the firms, not their customers, get to choose the jurisdiction whose laws will govern their transactions with customers.
Firms sort themselves into the jurisdictions that are most to their and their shareholders' liking.
It also turns out to be the socially optimal regime, as Ralph Winter and Roberta Romano have shown. Thus, the best, real federalism tort regime would let producers , rather than plaintiffs' lawyers, choose the jurisdiction. Proposals to this effect, alas, aren't even on the table. In some respects, on some issues, there is something to the intuition that a united front of state and local governments will help to promote federalism. As already suggested, however, the interest that principally unites state and local entities is a desire to remove federal barriers to organized looting.