California's new law requiring companies to include women on their boards of directors may not survive widely expected legal challenges but it has already spotlighted the entrenched practices and barriers that have helped keep women out of boardrooms.

Some of the country's best-known companies, along with many smaller ones, will have to overcome such obstacles to comply with the new measure, which requires public corporations headquartered in California to have at least one female director on their board by the end of next year.