There has been much discussion among various members of the design team regarding light pollution. Our understanding is that LEED states: no light traveling horizontally can pass the site property line, and that any light traveling in a vertical direction must be eliminated or blocked (you could uplight a covered bridge) so that no light escapes upwards into the sky. The Architect on this project wishes to uplight a translucent awning at the entrance of the building. All other exterior lighting will be downward. This architectural feature would be visible from above, however the translucent glass will diffuse the light, making the feature no brighter than downlight reflected off, say, concrete. Does the translucent awning make a sufficient light barrier by diffusing the uplight to eliminate light pollution?
It is possible to meet this credit with an uplit awning, provided you meet the requirements of IESNA Recommended Practice Manual: Lighting for Exterior Environments (RP-33). This standard lists specific illuminance values (uplight above the awning) that must not be exceeded by the project to capture this credit. In your case, you should make sure that all direct beam illumination is captured by the awning, and perform the calculations in RP-33 to demonstrate that you have met the IESNA standards. Applicable internationally.