Depends on the area and the issue. States are allowed in many cases to have control. For example in speed limits. States can have higher speed limits but may lose federal funding. Same with drinking laws and criminal laws. The federal government can put pressure on by withholding funding.
State laws can also be more generous. For example the federal law states that overtime is over 40 hours. A state can make it 35 but cannot make it 45.
Family Medical Leave Act - if the federal law says it affects employers with 75 employees, states can say 50 employees.
So......it really depends on the issue as to how much say a state has in the area. This is why civil rights violations, kidnapping and bank robbery are federal offenses. In this manner, the feds can step in even if the states don't have the same law or choose to look the other way or simply don't have the $ to pursue wrongdoers like in environmental protection matters.
