There are three basic ways that a job transfer, which does not include loss of pay or benefits, can be unlawful, which means, as the courts put it, that it constitutes an "adverse employment action." The three basic ways are as follows:
1) If the transfer would effectively constitute a demotion because of a "less distinguished title, a material loss of benefits, significantly diminished material responsibilities, or other indices that might be unique to a particular situation."this was how the United States Supreme Court described it in Burlington Northern Railway Company v. White, 548 U.S. 53 (2006).
2) Where the transfer amounts to a "constructive discharge." In order for an employee to be constructively discharged, a working conditions "must be objectively intolerable to a reasonable person." This means that working conditions are not just bad but really, really bad.
3) Where the transfer does not amount to a "constructive discharge" examples of which would include: where the employee shows a quantitative or qualitative change in the terms of the conditions of employment; where the new position is "more arduous and dirtier"; and, where an employee is transferred to "some wretched backwater." These are examples which will vary from case to case.
The key and ultimate issue is whether the transfer constitutes an "adverse employment action." This standard will vary from case to case, employee to employee.