That won't solve this problem. The military and government will do what is necessary to make sure the Guild of Software Engineers is officially completely fine with military applications.
This is something that only individuals can do.
And there will always be individuals willing to write this code, and that's not anything that can be solved by any number of Guilds either. The military will pay anything it takes to make it worth working outside of the Guild's rules.
Being able to say no with legal force is helpful even outside defense. I've discussed one of my previous roles unintentionally building an employee surveillance tool, and another codebase I contributed to is currently on the front page as a distant result of hurting people.
We can start with private enterprise, with ad tech, consumer data harvesting/surveillance and dark patterns targeting engagement and addiction. The military can be the last bastion to tackle once the guild has strength and can bargain to enforce guardrails. I'm looking at how SAG is so effective at navigating a multi-billion dollar entertainment industry filled with behemoths like Disney. If they can do it, we can too. At this point, the actors are looking smarter than software devs.
This is something that only individuals can do.
And there will always be individuals willing to write this code, and that's not anything that can be solved by any number of Guilds either. The military will pay anything it takes to make it worth working outside of the Guild's rules.