If this is about the "youth" bill in the Tokyo metropolitan government, it already passed and will take effect this spring, however, it doesn't actually ban anything, what it does is restrict access to adult content from minors in the Tokyo metropolitan area (which an existing, unenforced set of laws already governed). Many of the really unfortunate aspects of this new law are non-binding, meaning they're more "suggestions" to the industry, rather than imposing them to censor themselves or their content.
While I do not support this law in any way, I do understand the feelings behind it and the troublesome aspects of adult content's availability in Japan. Japan basically has two age ratings: Adult Only and Everything Else, meaning only clearly defined pornography is currently rated for adults only, and everything else, from G-rated all the way through R-rated content is not restricted. What prompted this law in Tokyo is indeed its hypocritical, sexist, xenophobic governor, but also a general unrest about the anime/manga industry's pushing of the limits of what is acceptable content, in particular in publications that are not age-rated, but are targetted towards a certain age group demographic.
This does clearly affect, if not target, BL, but the immediate effects probably won't be too severe. There'll be more ID checking in manga shops in Akihabara, and stuff that might have squeaked by in a YA magazine will be shifted to one targetted to an older audience. In the long term I don't see a law like this having any real teeth, considering it is one thing to establish culturally restrictive laws, and another entirely to enforce them. The general public that was either indifferent or supportive of the law was made to believe some half-truths about it and as the real truth about it comes out, there will more than likely be enough backlash to get the at least the worst parts of it repealed. What the industry really should do, though, is adopt a better age-rating system like most of the rest of the world already has.