If you agree that it doesn't say the government can, then it can't by default.
The Constitution specifically enumerates the classes of laws that Congress can pass. All other powers are reserved for the states.
I'm not a strict constructionist by any means (and I'm personally glad that we've set some shady precedents of the Commerce Clause and Necessary & Proper Clause allowing practically anything), but the Constitution makes it clear that unless a power is specifically given to the Federal Government, the Federal Government can't do it.
Yeah, that is true. However I am of the opinion that things like this are similar to minimum wage (which is also not mentioned in the Constitution) but can be mandated by Congress (though I could be wrong, is it done State by State?)
* Be able to point to some part of the Constitution that says (either directly or indirectly) that Congress can pass the law
* Coerce each state into passing the law, often by withholding funding from states that don't. This is how they raised the drinking age to 21, for example. Congress didn't pass a law saying "Persons under 21 may not drink", it passed a law saying "States that don't raise their drinking age to 21 will only get some percentage of the highway funding they would otherwise get." This method is very effective because federal grants make up about 25% of most states' budgets.
But most laws are passed in the first way. Justification often comes from the Commerce Clause (which gives Congress the authority to regulate interstate commerce. But today, unlike in 1787, basically everything is interstate commerce if you think about it right.).
Sometimes it also comes from the Neccessary & Proper (or Elastic) Clause, which says that Congress can pass any law that is "necessary and proper" for performing one of the other powers. It was basically there so that people wouldn't view the Constitution as listing the exact laws that Congress can be passed. For example, the Constitution never said "Congress may setup a national bank", but when people claimed that the law doing so was unconstitutional, Hamilton claimed that a national bank was necessary and proper for carrying out the powers of taxation and borrowing, which are given to Congress in the Constitution.
The Constitution specifically enumerates the classes of laws that Congress can pass. All other powers are reserved for the states.
I'm not a strict constructionist by any means (and I'm personally glad that we've set some shady precedents of the Commerce Clause and Necessary & Proper Clause allowing practically anything), but the Constitution makes it clear that unless a power is specifically given to the Federal Government, the Federal Government can't do it.