Puerto Rico is playing brinkmanship with creditors by threatening a default that could reverberate through financial markets and the refugee state of Florida. Congress may need to save the island from itself, if only to minimize the collateral damage.

On Wednesday Puerto Rico Governor Alejandro Garcia Padilla signed legislation authorizing him to declare a moratorium on the commonwealth’s $72 billion debt. This would trigger a default as soon as May when a $422 million payment on Government Development Bank debt comes due. Puerto Rico and its public agencies owe another $2 billion in July.

The moratorium upends negotiations with creditors and throws a wrench—perhaps deliberately—into Congressional deliberations over how to help the island manage the crisis. In a better world, Puerto Rico’s 18 public debt issuers, 20 some creditor committees and government unions would agree to a restructuring without federal intervention. But creditors possess competing claims, bond covenants conflict, and public agencies have intermingled funds. And Puerto Rico appears unwilling to act in good faith when left to its own devices.

Lo, last May Puerto Rico tripled its alternative minimum tax on corporations that transfer property from outside the commonwealth—in effect, a protective tariff. The tax’s lone target, Wal-Mart , sued. Puerto Rico claimed U.S. federal courts lack jurisdiction over its tax laws and that Wal-Mart had to pay before it could sue. That’s extortion.

Last week federal Judge José Antonio Fusté issued a scathing rebuke striking down the tax as a violation of the U.S. Constitution’s Commerce Clause. The tax, he wrote, was “a legislative money grab, pure and simple, funding the personal account of Puerto Rico’s insolvent Treasury from the presumably deeper pockets of large multistate corporations and their local affiliates.”