I think it would be a long road to get some of the major manufacturers to go along with not selling to, or providing law enforcement or military.
First, its the advertising that they get from getting their handgun adopted by, and carried by major law enforcement agencies. Glock did this extremely well in the past, which, I feel at least, is why they have a strong following around the country. Its not just the quality of the firearm, but the perception of that quality, in that, "it must be good since it was approved by so many agencies." So I think if this were done, it would basically stifle some newer designs that may come out.
Second, once the companies have lost these government contracts, it "can" be difficult for them to effectively compete for them in the future. It would probably narrow the market, in a way which would take a long time to re-open.
Lastly, the third is, I feel this will drive a deep dividing wedge between law enforcement and the public. While there are some exceptions in the current laws (and the propossed ones as well) for on-duty exemptions for LE, there is a small segment of the public that would like to either disarm LE or to restrict them to lesser firearms then is available to the general public.
While, unfortunatly the administration of some LE agencies are anti-gun, that doesnt mean that the rank-and-file is anti-gun also, and many of the rank-and-file support gun rights for everyone, so I feel its a way to divide firearm owners even more so.
To each their own though...