Who do we email to tell them to vote no?
You should locate the e-mail for your local Congessman first and e-mail them.
Then you should locate the e-mail for your Senator and e-mail them.
Additionally, if you have a few extra bucks around you could join the NRA. They not only keep track of this stuff, but they will send you quick and easy links on how to be active (like e-mailing your elected officials) to prevent just this type of legislation.