The Constitution reserves the right to declare war to Congress.
Obama and Kerry say they'll pretty much do whatever they want regardless of what Congress says.
Rand Paul says no.
Kerry says the world will be "safer" after the US bombs Syria. How is that going to work?
Civilians will almost certainly be killed in the process. Syria will become more hostile, not less. Tensions with Russia will become worse, not better. Religious extremists fighting against the government will become more powerful. Israel will be out at risk.