First, you or someone is mixing up the requirements for reasonable accommodation and family leave. It is the family leave laws that require an employer to return an employee to the same or substantially similar position after the leave expires.
The Family and Medical Leave Act, 29 U.S.C. section 2101 et seq. (FMLA) applies if all of the following is true: (a) your employer has at least 50 employees who work within 75 miles of one another; and (b) you have worked for this employer for at least one year all together, even if not consecutively; (c) you have worked for this employer at least 1,250 hours in the immediately preceding year; and (d) you have, or a spouse, parent or child has, a serious medical condition as defined by the FMLA. The FMLA allows employees to take leaves of absence from work without repercussion, up to a maximum of 12 weeks per year. Leave can be in increments as short as fractions of an hour. Please look at my Avvo guide on the Family and Medical Leave Act, 29 U.S.C. section 2101 et seq. (FMLA): http://www.avvo.com/pages/show?category_id=6&permalink=family-and-medical-leave-fmla-summary-of-key-provisions.
An employee or job applicant may have rights under the California Fair Employment and Housing Act, California Government Code sections 12900, et seq. (FEHA) and the Americans with Disabilities Act of 1990, 42 U.S.C. sections 12101 et seq. (ADA). The FEHA is a California law that is more employee-friendly than the ADA and which provides better remedies and better procedures.
FEHA applies to employers with at least 5 employees. To be eligible for protection of the FEHA, the employee or applicant must have a disability as defined by that law. This definition is “a physical or mental impairment that limits one or more major life activities.” The impairment must be permanent or of long duration, such as one year.
If these requirements are met, the employer may be required to provide reasonable accommodation. Reasonable accommodation may include transferring some non-essential job duties to other employees, providing equipment or devices to enable the employee to do the main functions of the job, allowing extra time off work for things related to the disability, and more. For applicants, the employer may need to provide reasonable accommodation in the form of extra time for qualification tests, better lighting, a proper chair, or any other modification that enables the applicant to apply.
Also, the employer may not treat an employee or applicant differently from other employees because of disability. For example, the employer may not refuse to hire or promote an individual, deny training or otherwise limit job opportunities, and the employer may not fire a person because of disability.
Please look at my Avvo guide on the ADA: http://www.avvo.com/pages/show?category_id=6&permalink=disability-discrimination-in-employment.
Please look at my Avvo guide to the differences between the ADA and California's more generous FEHA: http://www.avvo.com/legal-guides/ugc/employment-disability-protection-under-californias-fair-employment-and-housing-act-and-federal-ada?published=true.
Whether a leave of absence is a reasonable accommodation under the FEHA or ADA is an individualized assessment. It is based on the employer's resources, the employer's needs, the employee's limitations, and more. Any reasonable accommodation is appropriate as long as it is not a undue hardship on an employer. An "undue hardship" is a legal term of art that means providing the accommodation would be excessively expensive or disruptive to the employer's operations.
It is hard for me to think of a situation where a leave of absence for 18 months would NOT be an undue hardship on an employer. That is an extremely long time, and from the way you worded your question, it appears you have already been out on leave for a while and the 18 months is in addition to that.
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*** All legal actions have time limits, called statutes of limitation. If you miss the deadline for filing your claim, you will lose the opportunity to pursue your case. Please consult with an experienced employment attorney as soon as possible to better preserve your rights. *** Marilynn Mika Spencer provides information on Avvo as a service to the public, primarily when general information may be of assistance. Avvo is not an appropriate forum for an in-depth response or a detailed analysis. These comments are for information only and should not be considered legal advice. Legal advice must pertain to specific, detailed facts. No attorney-client relationship is created based on this information exchange. *** Marilynn Mika Spencer is licensed to practice law before all state and federal courts in California, and can appear before administrative agencies throughout the country. She is eligible to represent clients in other states on a pro hac vice basis. ***