congress can vote hoe they please on virtually anything but that doesn't mean that it becomes law. If their vote mandates something that is unconstitutional, the courts (equal power) would very soon rule against them.
Like Roe v. Wade?
Like Kelo v. City of New London
Like the 1934 National Firearms Act?
Like the Gun Control Act of 1968?
Like the Firearm Owners Protection Act of 1986?