Can this happen?
Certainly he can sign it, and senators can vote for it, and then it's off to the supreme court to discuss whether or not it can override the 2nd amendment. Thank goodness for Heller in that case because it will provide a precedent that individuals have a right to keep and bear arms (at least of some kind). Supreme court can be a bit of a crap shoot so you cross your fingers there.
What can you?
#1 item is agitate and advocate. Your vote alone is somewhat diluted in power, the votes you can bring to the table through activism are another matter. As much as folks tend to criticize the leftists of the late 20th century in their constant propaganda, protests, and activism, it has had a dramatic effect on the state of the nation's law and culture. You have just as much right to do the same to see your interests protected. To be effective you must learn the history and arguments. Learn what's in the writings and history relating to the founding of the nation. Learn the court history and what Miller 1939 was all about, and the "crime" bills in the 1980s/90s. Understand the opposition's goals and propaganda, be able to point out where they stretch the truth, but be able to recognize and discuss where pro-rights groups like the NRA stretch the truth from time to time as well. Review the history of gun control around the world, and how failure to protect the individual right to self-defense can create an environment favorable to genocide. Learn about self defense realities in the U.S. today. Then go out and write editorials, talk to your friends (in as supportive a way as possible), educate people and change their minds.
Suggested study materials:
www.guncite.com/
www.secondamendmentdocumentary.com/
www.thearmedcitizen.com/
#2 Join pro-rights organizations of a responsible character, adding your voice to many others.
#3 Support and advocate for candidates who recognize that an individual right to keep and bear arms, including "scary" guns is absolutely relevant to the security of a free state, and is a basic human right. Badger candidates that don't come all the way to this position, especially those who start talking about hunting when discussing the 2nd amendment. The 2nd amendment has nothing to do with hunting or sport shooting. Make it clear what needs to be protected.
#4 Keep things in perspective. The firearms crowd gets a perception aided by opposing propaganda of being fixated gun nuts for whom the need to own as many guns as possible and use them for anything. Drooling crazed gunfighters is the message anti-rights organizations paint. Don't give them rhetoric or behaviour that reinforces their stereotyping. Maintain deportment, stay realistic, be the image of public protection that we seek to maintain. People like and dislike the fellow who brought the AR-15 to a political rally a year or so ago. In some ways he was a bit too in your face for the general public and that wasn't entirely a help, but he was well dressed, well behaved, well spoken and gave a few people something to think about. Personally I wouldn't recommend taking guns to political rallies, but do look for opportunities to explain and demonstrate that guns in the right hands are an asset to public safety, not an automatic liability.
www.youtube.com/v/KfN7woo2xRY&hl=en_US
Also, the current administration, MSM, and leftwing activists are working full time to craft a narrative that conservatives, especially those who want to protect firearms rights are potential terrorists, revolutionaries, who want to tear down our constitutional system and represent a threat to the security of the state. Don't give them examples of speech or actions with which to justify stripping us of our rights. Keep a level head, and keep well grounded, and keep things in perspective. The goal is to preserve our human rights through maintaining protections like the 2nd amendment, and we still have a constitutional system in which to do that, and it's you that can make the difference by getting out there and convincing the people around you to vote for the people and initiatives that protect our civil rights.