May the States Block Illegal Immigration?

This post summarizes what earlier posts at this site have said about the states’ power to curb illegal immigration.
Understanding the Constitution: How States May Respond to Illegal Immigration—Part II

Under the Constitution, the states may wage defensive war without federal permission.
State over federal power: The 100th anniversary of the Colorado River Commission

The Colorado River Commission was one of the most successful conventions of states ever held. Its achievement debunks uninformed claims that interstate conventions are “unprecedented” or cannot follow a pre-set agenda.