Captive portal authentication ignores proxy

Setting the policy to Enabled lets Google Chrome OS bypass any proxy for captive portal authentication. These authentication webpages, starting from the captive portal sign-in page until Chrome detects a successful internet connection, open in a separate window, ignoring all policy settings and restrictions for the current user. This policy only takes effect if a proxy is set up (by policy, extension, or the user in chrome://settings).

Setting the policy to Disabled or leaving it unset means any captive portal authentication pages are shown in a (regular) new browser tab, using the current user's proxy settings.