Californian representative Jane Harman proposed a bill in the U.S. which could lead to a ban of inefficient light bulbs by 2012:
The bill (PDF), which was submitted by California representative Jane Harman, indicates that light bulbs which have an overall luminous efficacy of 60 lumens per watt (lm/W) will be prohibited by January 1, 2012. The energy requirements get progressively steeper every four years. On January 1, 2016, the requirement will grow to 90 lm/W and will reach 120 lm/W by 2020.
A traditional 100W tungsten incandescent light has an overall luminous efficacy of 17.5 lm/W. A 23W compact fluorescent (100W equivalent) has an overall luminous efficacy of 60 lm/W.
Exemptions could be made by the Secretary of Energy for certain applications where it wouldn't be feasible to use energy-efficient lighting. These include applications related to military, medical or matters of public safety.