Isn't it weird that a class of weapons can be deemed so terrible as to be banned in war, but remains legal for "law enforcement"?

That's not at all why it's banned in war. It's banned because the opposing side might mistake it for something like nerve gas, and then respond with something like nerve gas. Important to note that the chemical weapons treaty does NOT ban chemical weapons in war, it bans "first use."

(source, I took a class on Bioterrorism at RPI, which is still being taught apparently: http://catalog.rpi.edu/preview_course_nopop.php?catoid=8&coi... )

If it means less cops shooting at crowds thats all the justification you need as a politician.

Got any evidence to support that?