Colorado law saw a shift in the way that the State and the Federal government approach water rights. The law, which entered into force after a standard 90-day waiting period from its signing by Colorado's Governor Hickenlooper, makes key changes to the State's laws regarding the Feds.
The Law reaffirms the jurisdiction of Colorado Water Courts - which confirm allocations of water - over the Forest Service (USFS) and the Bureau of Land Management (BLM), in accordance with the McCarran Amendment which waived the Federal sovereign immunity for claims about water.
The Law instructs the State Engineer and Regional Engineers to refuse to implement any BLM or USFS title transfer of a water right, restriction on use or alienability of a water right, or mandate to a third-party to provide certain water for a specific time or use. In other words, the Federal government cannot use water without specific allocation by the State or the Water Courts.
The BLM or the USFS will be required to go to the State and request an allocation and have that allocation confirmed by the water courts before they can use it, even for a beneficial use. At least on organization has compared this new law as an exercise of State power akin to the Yucca Mountain nuclear disposal site dispute.
Colorado's approach seems to rest on the McCarran Amendment, primarily, begging the question of whether this new law would be an overstep of state authority if the McCarran Amendment were repealed by Congress. Given states' authority over water and the fact that the Amendment has been around since 1952, this seems unlikely. But it is not impossible if water scarcity nationwide becomes a significant threat to security.
For more information on the lead-up to this bill, check out this article.