Mandates and Their Impact upon the states
Financial burdens, esp. with unfunded mandates, e.g., ADA has imposed large costs upon states as they make "reasonable accommodations" for the disabled.
State complaints about federal heavy-handedness, e.g., if a state does not devise a plan and pay for the requirements of the Clean Air Act of 1990, the federal government will impose its own plan upon the state.
State complaints about federal blackmail, e.g., if a state doesn't comply with the Clean Air Act standards, federal funds can be withheld in other programs.