The U.S. Treasury Department and Internal Revenue Service finalized a rule last week defining decentralized finance platforms as brokers for tax-reporting purposes, a move cryptocurrency groups called industry-crippling and quickly challenged in court as violating constitutional rights to due process and protection against unreasonable searches.

Decentralized finance, or DeFi, platforms use blockchain technology to provide user-to-user financial services without going through intermediaries like banks or brokers. But the new IRS regulation requires DeFi platforms to collect and provide detailed transaction materials in tax returns as traditional brokers, because the agency stated that DeFi networks act as middlemen.