The GA rules are a set of rules used by the Secretariat to check if proposals are legal, illegal or should be discarded if they have serious rule violations. Of course, all site rules in the OSRS also apply to proposals. Here is a summary of the most important parts written by me (with some help of the forum post containing the full set of rules), so feel free to correct grammar or other errors if there are any:
Proposals are written as laws and have an operative clause;
They can create a committee, but it must interact with WA member nations, instead of just being created for nothing;
Proposals cannot:
Contradict or duplicate current resolutions;
Outlaw economic, political, religious, or other ideologies;
Rely on existing resolutions to support it (except for repeals);
Reference anything of the real world;
Break the 4th wall (meta-gaming), which is to refer to the NS world as part of a game;
Propose things that need a code change in the game;
Affect only a part of WA nations, or non-WA nations;
Mention the author as 'I', 'me', etc. (branding);
Plagiarise another player's proposal (the offending player will be ejected from the WA or even worse!)
Proposals can't be amended; instead they should be repealed and then written again;
Repeals can't do anything else than repeal the target resolution, and must be only submitted by the repeal link in the end of the target resolution;