Under the amendment proposed by Iowa Republican Representative Steve King, only the federal government could make laws establishing animal welfare practices for the agriculture industry.
In Arizona, that would prevent enforcement of the 2006 voter-approved law banning veal and pig gestation crates that raise the animals in extremely close quarters.
Paul Shapiro with the Humane Society of the United States points out there is no federal legislation pending that would replace state laws preempted by the amendment.
King's amendment is called the Protect Interstate Commerce Act and its supporters argue that having different laws for each state makes it difficult for large-scale producers. The U.S. House is expected to take up the Farm Bill and King's amendment today.