I hadn't really planned to do anything else about the light thing, but pfjunkie dug up what the cop was presumably talking about the other day. Here's the law that my neighbor is violating, from the El Paso Municipal Code:
18.18.270 Existing lighting causing light trespass onto residential property.
A. If after complaint and investigation, the director finds that an existing light fixture directs light toward residential buildings, the director shall give written notice of such violation to the owner and/or to the occupant of such premises demanding that the violation be abated within ninety days of the date of written notice.
B. Light trespass onto residential property from existing lighting shall be remedied by redirecting the light fixture or by controlling the light output as necessary.
C. Light levels shall not exceed a maximum of 0.25 footcandles (2.5 lux) at the property line of any residential property at a vertical point five feet above grade.
D. Light trespass measurements shall be made at the property line of the residential site, with the meter held normal to a line between any offending light source(s) and the light meter. If measurement on private property is not possible or practical, light level measurements may be made at the boundary of the public right of way or at any other location on an adjacent property.
E. Measurement shall be made using a commercial cosine and color corrected meter having an accuracy tolerance of plus or minus five percent or better at one lux (0.1 footcandle). The meter shall have been calibrated within two years of the date of measurement by the manufacturer or by a certified illumination laboratory.
F. Measurements shall be taken using a 4.5” long, 1.75” +/- 0.25” diameter thin wall black tube baffle atop the meter’s photoelectric cell aperture to prevent any stray light from other sources from affecting the measurement. (Ord. 15996 § A (part), 2005)
I think I might email one of the head inspectors I know in city hall. The cop we talked to seemed to think it was something the PD would get involved in, but usually stuff from the Building & Construction code is enforced by Building Inspectors. It won't hurt to check.