Only certain H-4 spouses will be able to obtain immigration employment authorization under the rule that should be effective around May 23rd, 2015:

· Are the principal beneficiaries of an approved Form I-140, Immigrant Petition for Alien Worker; or
· Have been granted H-1B status under sections 106(a) and (b) of the American Competitiveness in the Twenty-first Century Act of 2000 as amended by the 21st Century Department of Justice Appropriations Authorization Act. The Act permits H-1B nonimmigrants seeking lawful permanent residence to work and remain in the United States beyond the six-year limit on their H-1B status.

http://www.uscis.gov/news/dhs-extends-eligibility-employment-authorization-certain-h-4-dependent-spouses-h-1b-nonimmigrants-seeking-employment-based-lawful-permanent-residence

Some spouses of certain high-skilled immigrants working in the U.S. will soon be able to apply for work authorization of their own, the Obama administration is announcing Tuesday, February 24th. The change affects certain people with H-4 dependent spouse visas whose mates are seeking employment-based lawful permanent residence status, also known as a green card. They will be allowed to work while their spouses’ applications are processed. The regulation is being published on Wednesday and will take effect 90 days later.

http://blogs.wsj.com/washwire/2015/02/24/u-s-to-grant-work-permits-to-spouses-of-some-skilled-immigrants/